Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.
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Question: Freshwater below Earths surface is called groundwater. The water infiltrates, or seeps down into, the ground from the surface. How does this happen? And where does the water go? Water infiltrates the ground because soil and rock are porous. Between the grains are pores, or tiny holes. Since water can move through this rock it is permeable. Eventually, the water reaches a layer of rock that is not porous and so is impermeable. Water stops moving downward when it reaches this layer of rock. Look at the diagram in Figure 13.11. It shows two layers of porous rock. The top layer is not saturated; it is not full of water. The next layer is saturated. The water in this layer has nowhere else to go. It cannot seep any deeper into the ground because the rock below it is impermeable. The top of the saturated rock layer in Figure 13.11 is called the water table. The water table isnt like a real table. It doesnt remain firmly in one place. Instead, it rises or falls, depending on how much water seeps down from the surface. The water table is higher when there is a lot of rain and lower when the weather is dry. An underground layer of rock that is saturated with groundwater is called an aquifer. A diagram of an aquifer is shown in Figure 13.12. Aquifers are generally found in porous rock, such as sandstone. Water infiltrates the aquifer from the surface. The water that enters the aquifer is called recharge. Most land areas have aquifers beneath them. Many aquifers are used by people for freshwater. The closer to the surface an aquifer is, the easier it is to get the water. However, an aquifer close to the surface is also more likely to become polluted. Pollutants can seep down through porous rock in recharge water. An aquifer that is used by people may not be recharged as quickly as its water is removed. The water table may lower and the aquifer may even run dry. If this happens, the ground above the aquifer may sink. This is likely to damage any homes or other structures built above the aquifer. One of the biggest aquifers in the world is the Ogallala aquifer. As you can see from Figure 13.13, this aquifer lies beneath parts of eight U.S. states. It covers a total area of 451,000 square kilometers (174,000 square miles). In some places, it is less than a meter deep. In other places, it is hundreds of meters deep. The Ogallala aquifer is an important source of freshwater in the American Midwest. This is a major farming area, and much of the water is used to irrigate crops. The water in this aquifer is being used up ten times faster than it is recharged. If this continues, what might happen to the Ogallala aquifer? The top of an aquifer may be high enough in some places to meet the surface of the ground. This often happens on a slope. The water flows out of the ground and creates a spring. A spring may be just a tiny trickle, or it may be a big gush of water. One of the largest springs in the world is Big Spring in Missouri, seen in Figure 13.14. Water flowing out of the ground at a spring may flow downhill and enter a stream. Thats what happens to the water that flows out of Big Spring in Missouri. If the water from a spring cant flow downhill, it may spread out to form a pond or lake instead. Lake George in New York State, which is pictured in Figure 13.15, is a spring-fed lake. The lake basin was carved by a glacier. Some springs have water that contains minerals. Groundwater dissolves minerals out of the rock as it seeps through the pores. The water in some springs is hot because it is heated by hot magma. Many hot springs are also mineral springs. Thats because hot water can dissolve more minerals than cold water. Grand Prismatic Spring, shown in Figure 13.16, is a hot mineral spring. Dissolved minerals give its water a bright blue color. The edge of the spring is

Answer: top of an underground rock layer that is saturated with water


Question: Lighter and cheaper than high-quality video cameras, today's best smartphones can shoot and edit high-definition (HD) videos. With lower-quality lenses and image sensors, smartphones probably won't replace professional video cameras anytime soon. Still, some creative filmmakers are extending the borders of smartphone moviemaking by shooting professional-quality films using only smartphones. Soon after Apple's iPhone 4 was released, two filmmakers decided to make a short film using only their iPhone 4s. Michael Koerbel and Anna Elizabeth James shot and edited the one-and-a-half-minute film Apple of My Eye in only 48 hours. Audiences were fascinated with the film, in which a man and his grandfather connect emotionally while admiring a model train set in a store window. The filmmakers followed up their success with Goldilocks, an extraordinary spy novel told over nine, three-minute films. Many filmmakers are convinced that smartphone films are here to stay. One sign is their inclusion in major film festivals. In February 2012, organizers of the Berkshire International Film Festival staged the 10 X 10 On North Festival. Entries included Oliver by Hooman Khalili, an award-winning film about a girl whose special powers enable her to brighten the lives of three lonely people. Another entry was Yearlapse'11, a 365-second film by Zsolt Haraszti that describes an actual journey he made from New York to London. During the festival, which ran from February 16 to 26, these and many other smartphone films were shown at the Beacon Cinema in Pittsfield, Massachusetts. Similar festivals in Canada and South Korea have given smartphone filmmakers opportunities to show off their creative work.

Answer: Which film is about secret agents?


Question: Fish species are expected to shrink in size by up to 24% because of global warming, say scientists. The scientists argue that failure to control greenhouse gas emissions will have a greater effect on marine ecosystems than previously thought. Previous research has suggested that changing ocean temperatures would affect both the distribution and the reproductive abilities of many species of fish. This new work suggests that fish size would also be heavily affected. The researchers built a model to see how fish would react to lower levels of oxygen in the water. As ocean temperatures increase, so do the body temperatures of fish. But, according to lead author, Dr William Cheung, from the University of British Columbia, the lower level of oxygen in the water is key. Warmer waters could decrease ocean oxygen levels and greatly reduce fish body weight. On the other hand, rising temperatures directly increase the metabolic rate of the fish's body function. This leads to an increase in oxygen demand for normal body activities. So the fish will run out of oxygen for growth at a smaller body size. The research team also used its model to predict fish movements as a result of warming waters. The group believes that most fish populations will move towards the Earth's poles at a rate of up to 35km per decade. "So in, say, the North Sea," says Dr Cheung," one would expect to see more smaller-body fish from tropical waters in the future." Taking these factors into consideration, the research team concludes that fish body size will shrink between 14% and 24%, with the largest decreases in the Indian and Atlantic oceans. When compared with actual observations of fish sizes, the model seems to _ what's actually happening in the seas. The researchers looked at two case studies involving North Atlantic cod and haddock. They found that recorded data on these fish showed greater decreases in body size than the models had predicted. Dr Alan Baudron, from the University of Aberdeen, UK, believes smaller-sized fish could seriously affect the ability of fish to reproduce. "Smaller fish produce fewer and smaller eggs which could affect the reproductive potential of fish stocks," he said.

Answer:
What is the key factor making the fish smaller now?