nc33/multispan_quoref huggingface dataset:
In August 2003, cuts to funding by the Bogota Borough Council threaten the Bogota High School football team, enraging many residents. With a mayoral election ahead, the stage is set for a close election between the incumbent, Republican Steve Lonegan, and former Borough Council Democrat Fred Pesce. Then, in late September, former high school athlete Dave Musikant announces he will run for mayor as a write-in candidate. The three-way race garners national attention, particularly because both Lonegan and Musikant are legally blind. As election day draws near, Musikant scores a coup by hiring Doug Friedline, Jesse Ventura's former campaign manager. In the week before election day, a rumor develops that Pesce is ill and will drop out of the race. However, Pesce continues to the end.
As election day dawns, poor weather worries Lonegan, who fears low turnout may cause him to lose. However, Lonegan wins with 1,097 votes, while Pesce has 728, and Musikant has 200. The Republicans also win the City Council. That January, Lonegan is inaugurated as Mayor for his third term. The football team goes on to the state championship, but loses in that game. Pesce also announces his retirement from politics. In September 2004, Musikant succumbs to his eight-year battle with brain cancer. Lonegan goes on to run for the Republican nomination for governor that year, after Jim McGreevey's resignation, but loses the primary.

Question: What is the last name of the person who hires the former campaign manager of Jesse Ventura?
Answer: Musikant
In August 2003, cuts to funding by the Bogota Borough Council threaten the Bogota High School football team, enraging many residents. With a mayoral election ahead, the stage is set for a close election between the incumbent, Republican Steve Lonegan, and former Borough Council Democrat Fred Pesce. Then, in late September, former high school athlete Dave Musikant announces he will run for mayor as a write-in candidate. The three-way race garners national attention, particularly because both Lonegan and Musikant are legally blind. As election day draws near, Musikant scores a coup by hiring Doug Friedline, Jesse Ventura's former campaign manager. In the week before election day, a rumor develops that Pesce is ill and will drop out of the race. However, Pesce continues to the end.
As election day dawns, poor weather worries Lonegan, who fears low turnout may cause him to lose. However, Lonegan wins with 1,097 votes, while Pesce has 728, and Musikant has 200. The Republicans also win the City Council. That January, Lonegan is inaugurated as Mayor for his third term. The football team goes on to the state championship, but loses in that game. Pesce also announces his retirement from politics. In September 2004, Musikant succumbs to his eight-year battle with brain cancer. Lonegan goes on to run for the Republican nomination for governor that year, after Jim McGreevey's resignation, but loses the primary.

Question: What is the full name of the person that finishes last in the election?
Answer: Dave Musikant
In August 2003, cuts to funding by the Bogota Borough Council threaten the Bogota High School football team, enraging many residents. With a mayoral election ahead, the stage is set for a close election between the incumbent, Republican Steve Lonegan, and former Borough Council Democrat Fred Pesce. Then, in late September, former high school athlete Dave Musikant announces he will run for mayor as a write-in candidate. The three-way race garners national attention, particularly because both Lonegan and Musikant are legally blind. As election day draws near, Musikant scores a coup by hiring Doug Friedline, Jesse Ventura's former campaign manager. In the week before election day, a rumor develops that Pesce is ill and will drop out of the race. However, Pesce continues to the end.
As election day dawns, poor weather worries Lonegan, who fears low turnout may cause him to lose. However, Lonegan wins with 1,097 votes, while Pesce has 728, and Musikant has 200. The Republicans also win the City Council. That January, Lonegan is inaugurated as Mayor for his third term. The football team goes on to the state championship, but loses in that game. Pesce also announces his retirement from politics. In September 2004, Musikant succumbs to his eight-year battle with brain cancer. Lonegan goes on to run for the Republican nomination for governor that year, after Jim McGreevey's resignation, but loses the primary.

Question: What is the last name of the person who loses the primary for governor?
Answer: Lonegan
Ice drilling allows scientists studying glaciers and ice sheets to gain access to what is beneath the ice, to take measurements along the interior of the ice, and to retrieve samples.  Instruments can be placed in the drilled holes to record temperature, pressure, speed, direction of movement, and for other scientific research, such as neutrino detection.
Many different methods have been used since 1840, when the first scientific ice drilling expedition attempted to drill through the Unteraargletscher in the Alps.  Two early methods were percussion, in which the ice is fractured and pulverized, and rotary drilling, a method often used in mineral exploration for rock drilling.  In the 1940s, thermal drills began to be used; these drills melt the ice by heating the drill.  Drills that use jets of hot water or steam to bore through ice soon followed.  A growing interest in ice cores, used for palaeoclimatological research, led to ice coring drills being developed in the 1950s and 1960s, and there are now many different coring drills in use.  For obtaining ice cores from deep holes, most investigators use cable-suspended electromechanical drills, which use an armoured cable to carry electrical power to a mechanical drill at the bottom of the borehole.
In 1966, a US team successfully drilled through the Greenland ice sheet at Camp Century, at a depth of 1,387 metres (4,551 ft).  Since then many other groups have succeeded in reaching bedrock through the two largest ice sheets, in Greenland and Antarctica.  Recent projects have focused on finding drilling locations that will give scientists access to very old undisturbed ice at the bottom of the borehole, since an undisturbed stratigraphic sequence is required to accurately date the information obtained from the ice.

Question: Percussion and rotary drilling are two early methods of what?
Answer: Ice drilling
Ice drilling allows scientists studying glaciers and ice sheets to gain access to what is beneath the ice, to take measurements along the interior of the ice, and to retrieve samples.  Instruments can be placed in the drilled holes to record temperature, pressure, speed, direction of movement, and for other scientific research, such as neutrino detection.
Many different methods have been used since 1840, when the first scientific ice drilling expedition attempted to drill through the Unteraargletscher in the Alps.  Two early methods were percussion, in which the ice is fractured and pulverized, and rotary drilling, a method often used in mineral exploration for rock drilling.  In the 1940s, thermal drills began to be used; these drills melt the ice by heating the drill.  Drills that use jets of hot water or steam to bore through ice soon followed.  A growing interest in ice cores, used for palaeoclimatological research, led to ice coring drills being developed in the 1950s and 1960s, and there are now many different coring drills in use.  For obtaining ice cores from deep holes, most investigators use cable-suspended electromechanical drills, which use an armoured cable to carry electrical power to a mechanical drill at the bottom of the borehole.
In 1966, a US team successfully drilled through the Greenland ice sheet at Camp Century, at a depth of 1,387 metres (4,551 ft).  Since then many other groups have succeeded in reaching bedrock through the two largest ice sheets, in Greenland and Antarctica.  Recent projects have focused on finding drilling locations that will give scientists access to very old undisturbed ice at the bottom of the borehole, since an undisturbed stratigraphic sequence is required to accurately date the information obtained from the ice.

Question: Percussion and rotary drilling were two early methods of what?
Answer: Ice drilling
The ice must be cut through, broken up, or melted.  Tools can be directly pushed into snow and firn (snow that is compressed, but not yet turned to ice, which typically happens at a depth of 60 metres (200 ft) to 120 metres (390 ft)); this method is not effective in ice, but it is perfectly adequate for obtaining samples from the uppermost layers.  For ice, two options are percussion drilling and rotary drilling.  Percussion drilling uses a sharp tool such as a chisel, which strikes the ice to fracture and fragment it.  More common are rotary cutting tools, which have a rotating blade or set of blades at the bottom of the borehole to cut away the ice.  For small tools the rotation can be provided by hand, using a T-handle or a carpenter's brace.  Some tools can also be set up to make use of ordinary household power drills, or they may include a motor to drive the rotation.  If the torque is supplied from the surface, then the entire drill string must be rigid so that it can be rotated; but it is also possible to place a motor just above the bottom of the drill string, and have it supply power directly to the drill bit.If the ice is to be melted instead of cut, then heat must be generated.  An electrical heater built into the drill string can heat the ice directly, or it can heat the material it is embedded in, which in turn heats the ice.  Heat can also be sent down the drill string; hot water or steam pumped down from the surface can be used to heat a metal drillhead, or the water or steam can be allowed to emerge from the drillhead and melt the ice directly.  In at least one case a drilling project experimented with heating the drillhead on the surface, and then lowering it into the hole.Many ice drilling locations are very difficult to access, and drills must be designed so that they can be transported to the drill site.  The equipment should be as light and portable as possible.  It is helpful if the equipment can be broken down so that the individual components can be carried separately, thus reducing the burden for hand-carrying, if required.  Fuel, for steam or hot water drills, or for a generator to provide power, must also be transported, and this weight has to be taken into account as well.

Question: What object's weight has to be taken into account as well?
Answer: drills, Fuel
The ice must be cut through, broken up, or melted.  Tools can be directly pushed into snow and firn (snow that is compressed, but not yet turned to ice, which typically happens at a depth of 60 metres (200 ft) to 120 metres (390 ft)); this method is not effective in ice, but it is perfectly adequate for obtaining samples from the uppermost layers.  For ice, two options are percussion drilling and rotary drilling.  Percussion drilling uses a sharp tool such as a chisel, which strikes the ice to fracture and fragment it.  More common are rotary cutting tools, which have a rotating blade or set of blades at the bottom of the borehole to cut away the ice.  For small tools the rotation can be provided by hand, using a T-handle or a carpenter's brace.  Some tools can also be set up to make use of ordinary household power drills, or they may include a motor to drive the rotation.  If the torque is supplied from the surface, then the entire drill string must be rigid so that it can be rotated; but it is also possible to place a motor just above the bottom of the drill string, and have it supply power directly to the drill bit.If the ice is to be melted instead of cut, then heat must be generated.  An electrical heater built into the drill string can heat the ice directly, or it can heat the material it is embedded in, which in turn heats the ice.  Heat can also be sent down the drill string; hot water or steam pumped down from the surface can be used to heat a metal drillhead, or the water or steam can be allowed to emerge from the drillhead and melt the ice directly.  In at least one case a drilling project experimented with heating the drillhead on the surface, and then lowering it into the hole.Many ice drilling locations are very difficult to access, and drills must be designed so that they can be transported to the drill site.  The equipment should be as light and portable as possible.  It is helpful if the equipment can be broken down so that the individual components can be carried separately, thus reducing the burden for hand-carrying, if required.  Fuel, for steam or hot water drills, or for a generator to provide power, must also be transported, and this weight has to be taken into account as well.

Question: What type of tool should be as light and portable as possible?
Answer: drills
The ice must be cut through, broken up, or melted.  Tools can be directly pushed into snow and firn (snow that is compressed, but not yet turned to ice, which typically happens at a depth of 60 metres (200 ft) to 120 metres (390 ft)); this method is not effective in ice, but it is perfectly adequate for obtaining samples from the uppermost layers.  For ice, two options are percussion drilling and rotary drilling.  Percussion drilling uses a sharp tool such as a chisel, which strikes the ice to fracture and fragment it.  More common are rotary cutting tools, which have a rotating blade or set of blades at the bottom of the borehole to cut away the ice.  For small tools the rotation can be provided by hand, using a T-handle or a carpenter's brace.  Some tools can also be set up to make use of ordinary household power drills, or they may include a motor to drive the rotation.  If the torque is supplied from the surface, then the entire drill string must be rigid so that it can be rotated; but it is also possible to place a motor just above the bottom of the drill string, and have it supply power directly to the drill bit.If the ice is to be melted instead of cut, then heat must be generated.  An electrical heater built into the drill string can heat the ice directly, or it can heat the material it is embedded in, which in turn heats the ice.  Heat can also be sent down the drill string; hot water or steam pumped down from the surface can be used to heat a metal drillhead, or the water or steam can be allowed to emerge from the drillhead and melt the ice directly.  In at least one case a drilling project experimented with heating the drillhead on the surface, and then lowering it into the hole.Many ice drilling locations are very difficult to access, and drills must be designed so that they can be transported to the drill site.  The equipment should be as light and portable as possible.  It is helpful if the equipment can be broken down so that the individual components can be carried separately, thus reducing the burden for hand-carrying, if required.  Fuel, for steam or hot water drills, or for a generator to provide power, must also be transported, and this weight has to be taken into account as well.

Question: What may include a motor to drive the rotation?
Answer: Some tools
The ice must be cut through, broken up, or melted.  Tools can be directly pushed into snow and firn (snow that is compressed, but not yet turned to ice, which typically happens at a depth of 60 metres (200 ft) to 120 metres (390 ft)); this method is not effective in ice, but it is perfectly adequate for obtaining samples from the uppermost layers.  For ice, two options are percussion drilling and rotary drilling.  Percussion drilling uses a sharp tool such as a chisel, which strikes the ice to fracture and fragment it.  More common are rotary cutting tools, which have a rotating blade or set of blades at the bottom of the borehole to cut away the ice.  For small tools the rotation can be provided by hand, using a T-handle or a carpenter's brace.  Some tools can also be set up to make use of ordinary household power drills, or they may include a motor to drive the rotation.  If the torque is supplied from the surface, then the entire drill string must be rigid so that it can be rotated; but it is also possible to place a motor just above the bottom of the drill string, and have it supply power directly to the drill bit.If the ice is to be melted instead of cut, then heat must be generated.  An electrical heater built into the drill string can heat the ice directly, or it can heat the material it is embedded in, which in turn heats the ice.  Heat can also be sent down the drill string; hot water or steam pumped down from the surface can be used to heat a metal drillhead, or the water or steam can be allowed to emerge from the drillhead and melt the ice directly.  In at least one case a drilling project experimented with heating the drillhead on the surface, and then lowering it into the hole.Many ice drilling locations are very difficult to access, and drills must be designed so that they can be transported to the drill site.  The equipment should be as light and portable as possible.  It is helpful if the equipment can be broken down so that the individual components can be carried separately, thus reducing the burden for hand-carrying, if required.  Fuel, for steam or hot water drills, or for a generator to provide power, must also be transported, and this weight has to be taken into account as well.

Question: What object's weight has to be taken into account?
Answer: Fuel
The ice must be cut through, broken up, or melted.  Tools can be directly pushed into snow and firn (snow that is compressed, but not yet turned to ice, which typically happens at a depth of 60 metres (200 ft) to 120 metres (390 ft)); this method is not effective in ice, but it is perfectly adequate for obtaining samples from the uppermost layers.  For ice, two options are percussion drilling and rotary drilling.  Percussion drilling uses a sharp tool such as a chisel, which strikes the ice to fracture and fragment it.  More common are rotary cutting tools, which have a rotating blade or set of blades at the bottom of the borehole to cut away the ice.  For small tools the rotation can be provided by hand, using a T-handle or a carpenter's brace.  Some tools can also be set up to make use of ordinary household power drills, or they may include a motor to drive the rotation.  If the torque is supplied from the surface, then the entire drill string must be rigid so that it can be rotated; but it is also possible to place a motor just above the bottom of the drill string, and have it supply power directly to the drill bit.If the ice is to be melted instead of cut, then heat must be generated.  An electrical heater built into the drill string can heat the ice directly, or it can heat the material it is embedded in, which in turn heats the ice.  Heat can also be sent down the drill string; hot water or steam pumped down from the surface can be used to heat a metal drillhead, or the water or steam can be allowed to emerge from the drillhead and melt the ice directly.  In at least one case a drilling project experimented with heating the drillhead on the surface, and then lowering it into the hole.Many ice drilling locations are very difficult to access, and drills must be designed so that they can be transported to the drill site.  The equipment should be as light and portable as possible.  It is helpful if the equipment can be broken down so that the individual components can be carried separately, thus reducing the burden for hand-carrying, if required.  Fuel, for steam or hot water drills, or for a generator to provide power, must also be transported, and this weight has to be taken into account as well.

Question: What can heat the material it is embedded in?
Answer: An electrical heater
The ice must be cut through, broken up, or melted.  Tools can be directly pushed into snow and firn (snow that is compressed, but not yet turned to ice, which typically happens at a depth of 60 metres (200 ft) to 120 metres (390 ft)); this method is not effective in ice, but it is perfectly adequate for obtaining samples from the uppermost layers.  For ice, two options are percussion drilling and rotary drilling.  Percussion drilling uses a sharp tool such as a chisel, which strikes the ice to fracture and fragment it.  More common are rotary cutting tools, which have a rotating blade or set of blades at the bottom of the borehole to cut away the ice.  For small tools the rotation can be provided by hand, using a T-handle or a carpenter's brace.  Some tools can also be set up to make use of ordinary household power drills, or they may include a motor to drive the rotation.  If the torque is supplied from the surface, then the entire drill string must be rigid so that it can be rotated; but it is also possible to place a motor just above the bottom of the drill string, and have it supply power directly to the drill bit.If the ice is to be melted instead of cut, then heat must be generated.  An electrical heater built into the drill string can heat the ice directly, or it can heat the material it is embedded in, which in turn heats the ice.  Heat can also be sent down the drill string; hot water or steam pumped down from the surface can be used to heat a metal drillhead, or the water or steam can be allowed to emerge from the drillhead and melt the ice directly.  In at least one case a drilling project experimented with heating the drillhead on the surface, and then lowering it into the hole.Many ice drilling locations are very difficult to access, and drills must be designed so that they can be transported to the drill site.  The equipment should be as light and portable as possible.  It is helpful if the equipment can be broken down so that the individual components can be carried separately, thus reducing the burden for hand-carrying, if required.  Fuel, for steam or hot water drills, or for a generator to provide power, must also be transported, and this weight has to be taken into account as well.

Question: It is helpful if what tool can be broken down?
Answer: drills
Penetration testing involves inserting a probe into snow to determine the snow's mechanical properties.  Experienced snow surveyors can use an ordinary ski pole to test snow hardness by pushing it into the snow; the results are recorded based on the change in resistance felt as the pole is inserted.  A more scientific tool, invented in the 1930s but still in widespread use, is a ram penetrometer.  This takes the form of a rod with a cone at the lower end.  The upper end of the rod passes through a weight that is used as a hammer; the weight is lifted and released, and hits an anvil—a ledge around the rod which it cannot pass—which drives the rod into the snow.  To take a measurement, the rod is placed on the snow and the hammer is dropped one or more times; the resulting depth of penetration is recorded.  In soft snow a lighter hammer can be used to obtain more precise results; hammer weights range from 2 kg down to 0.1 kg.  Even with lighter hammers, ram penetrometers have difficulty distinguishing thin layers of snow, which limits their usefulness with regard to avalanche studies, since thin and soft layers are often involved in avalanche formation.Two lightweight tools are in wide use that are more sensitive than ram penetrometers.  A snow micro-penetrometer uses a motor to drive a rod into snow, measuring the force required; it is sensitive to 0.01–0.05 newtons, depending on the snow strength.  A SABRE probe consists of a rod that is inserted manually into snow; accelerometer readings are then used to determine the penetrative force needed at each depth, and stored electronically.For testing dense polar snow, a cone penetrometer test (CPT) is use, based on the equivalent devices used for soil testing.  CPT measurements can be used in hard snow and firn to depths of 5–10 m.

Question: What is the full name of the test whose measurements can be used in hard snow and firn to depths of 5–10 m?
Answer: a cone penetrometer test
Penetration testing involves inserting a probe into snow to determine the snow's mechanical properties.  Experienced snow surveyors can use an ordinary ski pole to test snow hardness by pushing it into the snow; the results are recorded based on the change in resistance felt as the pole is inserted.  A more scientific tool, invented in the 1930s but still in widespread use, is a ram penetrometer.  This takes the form of a rod with a cone at the lower end.  The upper end of the rod passes through a weight that is used as a hammer; the weight is lifted and released, and hits an anvil—a ledge around the rod which it cannot pass—which drives the rod into the snow.  To take a measurement, the rod is placed on the snow and the hammer is dropped one or more times; the resulting depth of penetration is recorded.  In soft snow a lighter hammer can be used to obtain more precise results; hammer weights range from 2 kg down to 0.1 kg.  Even with lighter hammers, ram penetrometers have difficulty distinguishing thin layers of snow, which limits their usefulness with regard to avalanche studies, since thin and soft layers are often involved in avalanche formation.Two lightweight tools are in wide use that are more sensitive than ram penetrometers.  A snow micro-penetrometer uses a motor to drive a rod into snow, measuring the force required; it is sensitive to 0.01–0.05 newtons, depending on the snow strength.  A SABRE probe consists of a rod that is inserted manually into snow; accelerometer readings are then used to determine the penetrative force needed at each depth, and stored electronically.For testing dense polar snow, a cone penetrometer test (CPT) is use, based on the equivalent devices used for soil testing.  CPT measurements can be used in hard snow and firn to depths of 5–10 m.

Question: What is the acronym for cone penetrometer test?
Answer: CPT
Drilling fluids are necessary for borehole stability in deep cores, and can also be used to circulate cuttings away from the bit.  Fluids used include water, ethanol/water and water/ethylene glycol mixtures, petroleum fuels, non-aromatic hydrocarbons, and n-butyl acetate.
Water is the cheapest and cleanest option; it may be present on the glacial surface or may be created by thermal drilling.  In cold ice some form of antifreeze is necessary, or heat must be reapplied by reaming the hole periodically.
Ethanol and water.  Ethanol acts as an anti-freeze in water; at sufficient concentrations it can reduce the freezing temperature of the mixture to well below any temperature likely to be encountered in ice drilling.  The concentration must be chosen to prevent the liquid freezing and also to maintain the borehole against the ice overburden pressure.  Because the density of the mixture decreases with lower temperatures, vertical convection will develop in boreholes where temperatures decrease with depth, as the lighter mixture rises.  This causes slush to form in the borehole, though successful drilling is still possible.  Ethanol is one of the cheapest options for a drilling fluid, and requires less storage space than other options because in use it is diluted with water.  A Soviet expedition left an 800 m borehole in Antarctica filled with ethanol and water at an ice temperature of −53 °C; after 11 months the borehole remained open and drilling was resumed with no problems.  A problem with this option is that the mixture will penetrate cores that have cracks.
Ethylene glycol and water was used at Camp Century in 1966 in the lower part of the hole to dissolve the cuttings.
Petroleum fuels.  This includes diesel, jet fuel, and kerosene. They are inexpensive and easily available, and were once in common use; disadvantages include flammability and the aromatics they contain, which are a health hazard.
Non-aromatic hydrocarbons.  As of 2009 these had become the most commonly used drilling fluids; eliminating the aromatics resolved the health issues with these fluids.  They are significantly more expensive than untreated petroleum fuels.
n-Butyl acetate.  A widely used fuel in the 1990s, because it is a close match for the density of ice, this is now unpopular because it dissolves many materials, which prevents their use in the drilling equipment it comes in contact with.  It is also flammable and corrosive, and protective clothing and in some cases masks may be necessary for people exposed to it.

Question: What is the name of the fluid for which eliminating the aromatics resolved the health issue?
Answer: Non-aromatic hydrocarbons
Drilling fluids are necessary for borehole stability in deep cores, and can also be used to circulate cuttings away from the bit.  Fluids used include water, ethanol/water and water/ethylene glycol mixtures, petroleum fuels, non-aromatic hydrocarbons, and n-butyl acetate.
Water is the cheapest and cleanest option; it may be present on the glacial surface or may be created by thermal drilling.  In cold ice some form of antifreeze is necessary, or heat must be reapplied by reaming the hole periodically.
Ethanol and water.  Ethanol acts as an anti-freeze in water; at sufficient concentrations it can reduce the freezing temperature of the mixture to well below any temperature likely to be encountered in ice drilling.  The concentration must be chosen to prevent the liquid freezing and also to maintain the borehole against the ice overburden pressure.  Because the density of the mixture decreases with lower temperatures, vertical convection will develop in boreholes where temperatures decrease with depth, as the lighter mixture rises.  This causes slush to form in the borehole, though successful drilling is still possible.  Ethanol is one of the cheapest options for a drilling fluid, and requires less storage space than other options because in use it is diluted with water.  A Soviet expedition left an 800 m borehole in Antarctica filled with ethanol and water at an ice temperature of −53 °C; after 11 months the borehole remained open and drilling was resumed with no problems.  A problem with this option is that the mixture will penetrate cores that have cracks.
Ethylene glycol and water was used at Camp Century in 1966 in the lower part of the hole to dissolve the cuttings.
Petroleum fuels.  This includes diesel, jet fuel, and kerosene. They are inexpensive and easily available, and were once in common use; disadvantages include flammability and the aromatics they contain, which are a health hazard.
Non-aromatic hydrocarbons.  As of 2009 these had become the most commonly used drilling fluids; eliminating the aromatics resolved the health issues with these fluids.  They are significantly more expensive than untreated petroleum fuels.
n-Butyl acetate.  A widely used fuel in the 1990s, because it is a close match for the density of ice, this is now unpopular because it dissolves many materials, which prevents their use in the drilling equipment it comes in contact with.  It is also flammable and corrosive, and protective clothing and in some cases masks may be necessary for people exposed to it.

Question: What is the name of that which had become the most commonly used drilling fluid by 2009?
Answer: Non-aromatic hydrocarbons
Drilling fluids are necessary for borehole stability in deep cores, and can also be used to circulate cuttings away from the bit.  Fluids used include water, ethanol/water and water/ethylene glycol mixtures, petroleum fuels, non-aromatic hydrocarbons, and n-butyl acetate.
Water is the cheapest and cleanest option; it may be present on the glacial surface or may be created by thermal drilling.  In cold ice some form of antifreeze is necessary, or heat must be reapplied by reaming the hole periodically.
Ethanol and water.  Ethanol acts as an anti-freeze in water; at sufficient concentrations it can reduce the freezing temperature of the mixture to well below any temperature likely to be encountered in ice drilling.  The concentration must be chosen to prevent the liquid freezing and also to maintain the borehole against the ice overburden pressure.  Because the density of the mixture decreases with lower temperatures, vertical convection will develop in boreholes where temperatures decrease with depth, as the lighter mixture rises.  This causes slush to form in the borehole, though successful drilling is still possible.  Ethanol is one of the cheapest options for a drilling fluid, and requires less storage space than other options because in use it is diluted with water.  A Soviet expedition left an 800 m borehole in Antarctica filled with ethanol and water at an ice temperature of −53 °C; after 11 months the borehole remained open and drilling was resumed with no problems.  A problem with this option is that the mixture will penetrate cores that have cracks.
Ethylene glycol and water was used at Camp Century in 1966 in the lower part of the hole to dissolve the cuttings.
Petroleum fuels.  This includes diesel, jet fuel, and kerosene. They are inexpensive and easily available, and were once in common use; disadvantages include flammability and the aromatics they contain, which are a health hazard.
Non-aromatic hydrocarbons.  As of 2009 these had become the most commonly used drilling fluids; eliminating the aromatics resolved the health issues with these fluids.  They are significantly more expensive than untreated petroleum fuels.
n-Butyl acetate.  A widely used fuel in the 1990s, because it is a close match for the density of ice, this is now unpopular because it dissolves many materials, which prevents their use in the drilling equipment it comes in contact with.  It is also flammable and corrosive, and protective clothing and in some cases masks may be necessary for people exposed to it.

Question: What is the name of the drilling fluid that is significantly more expensive than untreated petroleum fuels?
Answer: Non-aromatic hydrocarbons
Drilling fluids are necessary for borehole stability in deep cores, and can also be used to circulate cuttings away from the bit.  Fluids used include water, ethanol/water and water/ethylene glycol mixtures, petroleum fuels, non-aromatic hydrocarbons, and n-butyl acetate.
Water is the cheapest and cleanest option; it may be present on the glacial surface or may be created by thermal drilling.  In cold ice some form of antifreeze is necessary, or heat must be reapplied by reaming the hole periodically.
Ethanol and water.  Ethanol acts as an anti-freeze in water; at sufficient concentrations it can reduce the freezing temperature of the mixture to well below any temperature likely to be encountered in ice drilling.  The concentration must be chosen to prevent the liquid freezing and also to maintain the borehole against the ice overburden pressure.  Because the density of the mixture decreases with lower temperatures, vertical convection will develop in boreholes where temperatures decrease with depth, as the lighter mixture rises.  This causes slush to form in the borehole, though successful drilling is still possible.  Ethanol is one of the cheapest options for a drilling fluid, and requires less storage space than other options because in use it is diluted with water.  A Soviet expedition left an 800 m borehole in Antarctica filled with ethanol and water at an ice temperature of −53 °C; after 11 months the borehole remained open and drilling was resumed with no problems.  A problem with this option is that the mixture will penetrate cores that have cracks.
Ethylene glycol and water was used at Camp Century in 1966 in the lower part of the hole to dissolve the cuttings.
Petroleum fuels.  This includes diesel, jet fuel, and kerosene. They are inexpensive and easily available, and were once in common use; disadvantages include flammability and the aromatics they contain, which are a health hazard.
Non-aromatic hydrocarbons.  As of 2009 these had become the most commonly used drilling fluids; eliminating the aromatics resolved the health issues with these fluids.  They are significantly more expensive than untreated petroleum fuels.
n-Butyl acetate.  A widely used fuel in the 1990s, because it is a close match for the density of ice, this is now unpopular because it dissolves many materials, which prevents their use in the drilling equipment it comes in contact with.  It is also flammable and corrosive, and protective clothing and in some cases masks may be necessary for people exposed to it.

Question: What is the name of that which is a close match for the density of ice, which encouraged its widespread use in the 1990s?
Answer: n-Butyl acetate
Drilling fluids are necessary for borehole stability in deep cores, and can also be used to circulate cuttings away from the bit.  Fluids used include water, ethanol/water and water/ethylene glycol mixtures, petroleum fuels, non-aromatic hydrocarbons, and n-butyl acetate.
Water is the cheapest and cleanest option; it may be present on the glacial surface or may be created by thermal drilling.  In cold ice some form of antifreeze is necessary, or heat must be reapplied by reaming the hole periodically.
Ethanol and water.  Ethanol acts as an anti-freeze in water; at sufficient concentrations it can reduce the freezing temperature of the mixture to well below any temperature likely to be encountered in ice drilling.  The concentration must be chosen to prevent the liquid freezing and also to maintain the borehole against the ice overburden pressure.  Because the density of the mixture decreases with lower temperatures, vertical convection will develop in boreholes where temperatures decrease with depth, as the lighter mixture rises.  This causes slush to form in the borehole, though successful drilling is still possible.  Ethanol is one of the cheapest options for a drilling fluid, and requires less storage space than other options because in use it is diluted with water.  A Soviet expedition left an 800 m borehole in Antarctica filled with ethanol and water at an ice temperature of −53 °C; after 11 months the borehole remained open and drilling was resumed with no problems.  A problem with this option is that the mixture will penetrate cores that have cracks.
Ethylene glycol and water was used at Camp Century in 1966 in the lower part of the hole to dissolve the cuttings.
Petroleum fuels.  This includes diesel, jet fuel, and kerosene. They are inexpensive and easily available, and were once in common use; disadvantages include flammability and the aromatics they contain, which are a health hazard.
Non-aromatic hydrocarbons.  As of 2009 these had become the most commonly used drilling fluids; eliminating the aromatics resolved the health issues with these fluids.  They are significantly more expensive than untreated petroleum fuels.
n-Butyl acetate.  A widely used fuel in the 1990s, because it is a close match for the density of ice, this is now unpopular because it dissolves many materials, which prevents their use in the drilling equipment it comes in contact with.  It is also flammable and corrosive, and protective clothing and in some cases masks may be necessary for people exposed to it.

Question: What is the name of the drilling fluid that is now unpopular because it dissolves many materials, which prevents their use in the drilling equipment it comes in contact with?
Answer: n-Butyl acetate
Drilling fluids are necessary for borehole stability in deep cores, and can also be used to circulate cuttings away from the bit.  Fluids used include water, ethanol/water and water/ethylene glycol mixtures, petroleum fuels, non-aromatic hydrocarbons, and n-butyl acetate.
Water is the cheapest and cleanest option; it may be present on the glacial surface or may be created by thermal drilling.  In cold ice some form of antifreeze is necessary, or heat must be reapplied by reaming the hole periodically.
Ethanol and water.  Ethanol acts as an anti-freeze in water; at sufficient concentrations it can reduce the freezing temperature of the mixture to well below any temperature likely to be encountered in ice drilling.  The concentration must be chosen to prevent the liquid freezing and also to maintain the borehole against the ice overburden pressure.  Because the density of the mixture decreases with lower temperatures, vertical convection will develop in boreholes where temperatures decrease with depth, as the lighter mixture rises.  This causes slush to form in the borehole, though successful drilling is still possible.  Ethanol is one of the cheapest options for a drilling fluid, and requires less storage space than other options because in use it is diluted with water.  A Soviet expedition left an 800 m borehole in Antarctica filled with ethanol and water at an ice temperature of −53 °C; after 11 months the borehole remained open and drilling was resumed with no problems.  A problem with this option is that the mixture will penetrate cores that have cracks.
Ethylene glycol and water was used at Camp Century in 1966 in the lower part of the hole to dissolve the cuttings.
Petroleum fuels.  This includes diesel, jet fuel, and kerosene. They are inexpensive and easily available, and were once in common use; disadvantages include flammability and the aromatics they contain, which are a health hazard.
Non-aromatic hydrocarbons.  As of 2009 these had become the most commonly used drilling fluids; eliminating the aromatics resolved the health issues with these fluids.  They are significantly more expensive than untreated petroleum fuels.
n-Butyl acetate.  A widely used fuel in the 1990s, because it is a close match for the density of ice, this is now unpopular because it dissolves many materials, which prevents their use in the drilling equipment it comes in contact with.  It is also flammable and corrosive, and protective clothing and in some cases masks may be necessary for people exposed to it.

Question: What is the name of the drilling fluid for which protective clothing, and in some cases masks, may be necessary for people exposed to it due to its flammability and corrosiveness?
Answer: n-Butyl acetate
Drilling fluids are necessary for borehole stability in deep cores, and can also be used to circulate cuttings away from the bit.  Fluids used include water, ethanol/water and water/ethylene glycol mixtures, petroleum fuels, non-aromatic hydrocarbons, and n-butyl acetate.
Water is the cheapest and cleanest option; it may be present on the glacial surface or may be created by thermal drilling.  In cold ice some form of antifreeze is necessary, or heat must be reapplied by reaming the hole periodically.
Ethanol and water.  Ethanol acts as an anti-freeze in water; at sufficient concentrations it can reduce the freezing temperature of the mixture to well below any temperature likely to be encountered in ice drilling.  The concentration must be chosen to prevent the liquid freezing and also to maintain the borehole against the ice overburden pressure.  Because the density of the mixture decreases with lower temperatures, vertical convection will develop in boreholes where temperatures decrease with depth, as the lighter mixture rises.  This causes slush to form in the borehole, though successful drilling is still possible.  Ethanol is one of the cheapest options for a drilling fluid, and requires less storage space than other options because in use it is diluted with water.  A Soviet expedition left an 800 m borehole in Antarctica filled with ethanol and water at an ice temperature of −53 °C; after 11 months the borehole remained open and drilling was resumed with no problems.  A problem with this option is that the mixture will penetrate cores that have cracks.
Ethylene glycol and water was used at Camp Century in 1966 in the lower part of the hole to dissolve the cuttings.
Petroleum fuels.  This includes diesel, jet fuel, and kerosene. They are inexpensive and easily available, and were once in common use; disadvantages include flammability and the aromatics they contain, which are a health hazard.
Non-aromatic hydrocarbons.  As of 2009 these had become the most commonly used drilling fluids; eliminating the aromatics resolved the health issues with these fluids.  They are significantly more expensive than untreated petroleum fuels.
n-Butyl acetate.  A widely used fuel in the 1990s, because it is a close match for the density of ice, this is now unpopular because it dissolves many materials, which prevents their use in the drilling equipment it comes in contact with.  It is also flammable and corrosive, and protective clothing and in some cases masks may be necessary for people exposed to it.

Question: What is the name of the classification of drilling fluids, among them kerosene, whose disadvantages include flammability and the aromatics they contain, which are a health hazard?
Answer: Petroleum fuels
Drilling fluids are necessary for borehole stability in deep cores, and can also be used to circulate cuttings away from the bit.  Fluids used include water, ethanol/water and water/ethylene glycol mixtures, petroleum fuels, non-aromatic hydrocarbons, and n-butyl acetate.
Water is the cheapest and cleanest option; it may be present on the glacial surface or may be created by thermal drilling.  In cold ice some form of antifreeze is necessary, or heat must be reapplied by reaming the hole periodically.
Ethanol and water.  Ethanol acts as an anti-freeze in water; at sufficient concentrations it can reduce the freezing temperature of the mixture to well below any temperature likely to be encountered in ice drilling.  The concentration must be chosen to prevent the liquid freezing and also to maintain the borehole against the ice overburden pressure.  Because the density of the mixture decreases with lower temperatures, vertical convection will develop in boreholes where temperatures decrease with depth, as the lighter mixture rises.  This causes slush to form in the borehole, though successful drilling is still possible.  Ethanol is one of the cheapest options for a drilling fluid, and requires less storage space than other options because in use it is diluted with water.  A Soviet expedition left an 800 m borehole in Antarctica filled with ethanol and water at an ice temperature of −53 °C; after 11 months the borehole remained open and drilling was resumed with no problems.  A problem with this option is that the mixture will penetrate cores that have cracks.
Ethylene glycol and water was used at Camp Century in 1966 in the lower part of the hole to dissolve the cuttings.
Petroleum fuels.  This includes diesel, jet fuel, and kerosene. They are inexpensive and easily available, and were once in common use; disadvantages include flammability and the aromatics they contain, which are a health hazard.
Non-aromatic hydrocarbons.  As of 2009 these had become the most commonly used drilling fluids; eliminating the aromatics resolved the health issues with these fluids.  They are significantly more expensive than untreated petroleum fuels.
n-Butyl acetate.  A widely used fuel in the 1990s, because it is a close match for the density of ice, this is now unpopular because it dissolves many materials, which prevents their use in the drilling equipment it comes in contact with.  It is also flammable and corrosive, and protective clothing and in some cases masks may be necessary for people exposed to it.

Question: What is the name of the specific category of drilling fluid that includes includes diesel, jet fuel, and kerosene?
Answer: Petroleum fuels