Vervet monkeys use different alarm calls to warn each other of nearby predators, depending on whether the danger comes from land or from the air. Which one of the following, if true, contributes most to an explanation of the behavior of vervet monkeys described above? A. By varying the pitch of its alarm call, a vervet monkey can indicate the number of predators approaching. B. Different land-based predators are responsible for different numbers of vervet monkey deaths. C. No predators that pose a danger to vervet monkeys can attack both from land and from the air. D. Vervet monkeys avoid land-based predators by climbing trees but avoid predation from the air by diving into foliage. E. Certain land-based predators feed only on vervet monkeys, whereas every predator that attacks vervet monkeys from the air feeds on many different animals. -- by 会员 blvicky (2009/12/12 16:49:15)
明显选D
题目说vm根据危险来源的不同采用不同的警告声，问解释
d最合理，只有不同的警告声暗示不同的做法才有意义，不然用一种就够了
个人建议lz以后出题直接给出答案，反正是供大家讨论的：） | 
京公网安备11010202008513号 京ICP证101109号 京ICP备12012021号
发表于 2009-12-14 11:32:05
楼主
