单选题 Dr. Brosnan and Dr. de Waal have eventually found in their study that the monkeys ______.

A、 prefer grapes to cucumbers
B、 can be taught to exchange things
C、 will not be co-operative if feeling cheated
D、 are unhappy when separated from others

【正确答案】 C

【答案解析】[题型分析] 细节题 [详细解答] 根据问题中的线索词“eventually”，可以确定这道题所对应的出题句可能在最后一段。事实上，它对应的是末段第二句“Such co-operation is likely to be stable only when each animal feels it is not being cheated，”C选项说到的正好是这个意思。所以，C选项是正确答案。