You are given a background paragraph that describes one or more causal or qualitative relationships such as a relationship in economics or a scientific law and a story that makes use of the concepts or the relationship described in the provided paragraph. You are also given a question about the story that requires an understanding of the relationship described in the background paragraph and the story. You need to come up with an answer to the given question; the answer will be a span from either the question or the story. In order to correctly answer the given question, you need to understand the relationship mentioned in the background paragraph and should be able to use it to understand that in the story. Your answer can not consist of any word that is not mentioned in any of these: the background paragraph, the story, or the question. You can directly copy and paste a span from the story or the question while answering the given question.

[Q]: Background Paragraph: Alpine climate is the average weather (climate) for the alpine tundra. The climate becomes colder at high elevationsthis characteristic is described by the lapse rate of air: air tends to get colder as it rises, since it expands. The dry adiabatic lapse rate is 10 C per km (5.5 F per 1000 ft) of elevation or altitude. Therefore, moving up 100 metres (330 ft) on a mountain is roughly equivalent to moving 80 kilometers (45 miles or 0.75 of latitude) towards the pole. This relationship is only approximate, however, since local factors such as proximity to oceans can drastically modify the climate.
Story: Two meteorologists study Earth's climate. Jerry studies alpine climate, while James studies tropical climates. They both made great progress.
Question: Which person learned more about the lapse rate of air?
[A]: Jerry.

[Q]: Background Paragraph: In nature, when the population size is small, there is usually plenty of food and other resources for each individual. When there is plenty of food and other resources, organisms can easily reproduce, so the birth rate is high. As the population increases, the food supply, or the supply of another necessary resource, may decrease. When necessary resources, such as food, decrease, some individuals will die. Overall, the population cannot reproduce at the same rate, so the birth rates drop. This will cause the population growth rate to decrease.
Story: Two neighboring countries of similar size and wealth of resources had different sized population. Deerland had a small population, while Bearland had a large population. Both peoples lived mostly off the land.
Question: Which country had plenty of resources per individual?
[A]: Deerland.

[Q]: Background Paragraph: Einstein showed in his thought experiments that people travelling at different speeds, while agreeing on cause and effect, measure different time separations between events, and can even observe different chronological orderings between non-causally related events. Though these effects are typically minute in the human experience, the effect becomes much more pronounced for objects moving at speeds approaching the speed of light. Subatomic particles exist for a well known average fraction of a second in a lab relatively at rest, but when travelling close to the speed of light they are measured to travel farther and exist for much longer than when at rest. According to the special theory of relativity, in the high-speed particle's frame of reference, it exists, on the average, for a standard amount of time known as its mean lifetime, and the distance it travels in that time is zero, because its velocity is zero. Relative to a frame of reference at rest, time seems to "slow down" for the particle. Relative to the high-speed particle, distances seem to shorten. Einstein showed how both temporal and spatial dimensions can be altered (or "warped") by high-speed motion.
Story: David wanted to test the theory of Einstein. To that end, he measured the time perceived by an airline pilot, who naturally traveled very fast. He labeled it as case A. To compare the pilot with a slower traveler he measured the time perceived by a semi truck driver covering the same distance. He labeled it as case B. He was amazed by the counter intuitive results he got from the experiment.
Question: According to Einstein, who would perceive "slow down" of time, case A or case B?
[A]:
case A.