daretodream wrote:The energy an animal must expend to move uphill is proportional to its body weight, whereas the animal's energy output available to perform this task is proportional to its surface area. This is the reason that small animals, like squirrel, can run up a tree trunk almost as fast as they can move on level ground, whereas large animals tend to slow down when they are moving uphill.
Which one of the following is an assumption on which the explanation above depends?
(A) The amount of energy needed to move uphill is no greater for large animals that it is for small animals.
this is opposite and hence counter the argument[spoiler]

(B)[/spoiler] Small animals can move more rapidly than large animals can.
scope shift type a/c: it's not about the speed of large animals to small animals, it's about speed of each in uphill in compared with each' speed in flat ground

(C) The ratio of surface area to body weight is smaller in large animals than it is in small animals.
correct:Because such ratio of large animals is not equal to that of small animals, large animals can;t remain its speed when moving uphill as can small animals when moving uphill

(D) There is little variation in the ratio of energy output to body weight among animals.
does not effects the conclusion

(E) The amount of energy needed to run at a given speed is proportional to the surface area of the running animal.
irrelevant

B