Answer the following question given this paragraph: The axon of many neurons has an outer layer called a myelin sheath (see Figure above ). Myelin is a lipid produced by a type of a glial cell known as a Schwann cell. The myelin sheath acts like a layer of insulation, similar to the plastic that encases an electrical cord. Regularly spaced nodes, or gaps, in the myelin sheath allow nerve impulses to skip along the axon very rapidly. Q: What is the outer layer of an axon that acts like a layer of insulation, similar to the plastic that encases an electrical cord? A:
OPTIONS:
- lipids sheath
- nerve sheath
- layer sheath
- myelin sheath
myelin sheath

Answer the following question given this paragraph: There are other measurable characteristics of a gas. One of them is temperature (T). Perhaps one can vary the temperature of a gas sample and note what effect it has on the other properties of the gas. Early scientists did just this, discovering that if the amount of a gas and its pressure are kept constant, then changing the temperature changes the volume (V). As temperature increases, volume increases; as temperature decreases, volume decreases. We say that these two characteristics are directly related. A mathematical relationship between V and T should be possible except for one thought: what temperature scale should we use? We know from Chapter 2 "Measurements" that science uses several possible temperature scales. Experiments show that the volume of a gas is related to its absolute temperature in Kelvin, not its temperature in degrees Celsius. If the temperature of a gas is expressed in kelvins, then experiments show that the ratio of volume to temperature is a constant:. Q: What happens to the volume of the gas when temperature increases but amount of gas and its pressure are constant? A:
OPTIONS:
- nothing
- volume remains constant
- volume decreases
- volume increases

Answer: volume increases

Question: Answer the following question given this paragraph: A machine is any device that makes work easier by changing a force. When you use a machine, you apply force to the machine. This force is called the input force. The machine, in turn, applies force to an object. This force is called the output force. Recall that work equals force multiplied by distance:. Q: A machine is any device that makes work easier by doing what? A:
OPTIONS:
- moving things
- changing molecules
- removing barriers
- changing a force
Answer: changing a force

input with options: Answer the following question given this paragraph: Gases in the coma and tail of a comet reflect light from the Sun. Comets are very hard to see except when they have comas and tails. That is why they appear only when they are near the Sun. They disappear again as they move back to the outer solar system. Q: What parts of comets make them easy to see? A:
OPTIONS:
- arcs and tails
- novas and tails
- craters and tails
- comas and tails
output: comas and tails

Q: Answer the following question given this paragraph: Predator species such as birds and spiders control insect pests. They reduce the need for chemical pesticides, which are expensive and may be harmful to human beings and other organisms. Q: Predators can replace what tool in agriculture. A:

OPTIONS:
- harvesters
- fertilizer
- irrigators
- pesticides

A: pesticides

Answer the following question given this paragraph: atoms held together by covalent bonds; they tend to be very hard and have high melting points. Metallic solids have unusual properties: in addition to having high thermal and electrical conductivity and being malleable and ductile, they exhibit luster, a shiny surface that reflects light. An alloy is a mixture of metals that has bulk metallic properties different from those of its constituent elements. Alloys can be formed by substituting one metal atom for another of similar size in the lattice (substitutional alloys), by inserting smaller atoms into holes in the metal lattice (interstitial alloys), or by a combination of both. Although the elemental composition of most alloys can vary over wide ranges, certain metals combine in only fixed proportions to form intermetallic compounds with unique properties. Q: An alloy is a mixture of metals that has bulk metallic properties different from those of its what? A:
OPTIONS:
- system elements
- nuclear elements
- mineral elements
- constituent elements
constituent elements