OE for reference:
Overview:The passage describes the responses of Jocko, a chimpanzee, to receiving bananas while alone. When Jocko was given a large bunch of bananas, he made loud "food barks," which caused other chimpanzees to come and take the bananas. Later, Jocko was given a a single banana and kept quiet. A zookeeper concluded that Jocko kept quiet so that other chimpanzees wouldn't take the banana. You are asked to find the statement that most seriously calls this conclusion into question.
The Correct Answer:B According to (B), chimpanzees only utter food barks when a sizable quantity of food is present. This suggests an alternative explanation for Jocko's behavior: he did not make food barks when given a single banana because one banana—unlike a large bunch of bananas—is not enough to elicit a food bark. Since (B) shows that the information in the passage is consistent with a completely different account of Jocko's behavior, the zookeeper’s conclusion is called into question.
The Incorrect Answer Choices:A (A) says that chimpanzees only make food barks when their favorite foods are present. Even if this explains why Jocko made food barks when given many bananas, it doesn’t challenge the zookeeper's conclusion, because it doesn’t explain why Jocko kept silent when given a single banana.
C (C) offers an explanation for the behavior of chimpanzees who take food from other chimpanzees. Since Jocko did not take any food from other chimpanzees, (C) does not call into question the zookeeper's conclusion about Jocko's behavior.
D (D) tells us that chimpanzees often make noises that appear to be signals to other chimpanzees even when no other chimpanzees are present. This is not relevant to the zookeeper’s conclusion, which purports to explain why Jocko did
not make noises when given a single banana.
E According to (E), all of the zoo's chimpanzees show a strong preference for bananas. This is entirely consistent with the zookeeper's conclusion about Jocko's behavior, since it would suggest that Jocko had a good reason to keep quiet in order to keep other chimpanzees from taking his banana.