参考答案是A －The body temperatures of warm-blooded animals cannot be easily controlled in the laboratory.
但是原文中只有“Cold-blooded animals were used to test this hypothesis because their body temperature can be controlled in the laboratory.” 根据这句话，我有命题1如下： If the animal is a cold-blood animal, then its body temperature can be controlled in the laboratory. 而以上命题1的逆否命题命题2应该和本命题等价，即（命题2）： If its body temperature can not be controlled in the laboratory, then it is not a cold-blood animal. 再根据定义，not cold-blood animal即为warm-blood animal，我得出命题3： If its body temperature can not be controlled in the laboratory, then it is a warm-blood animal.
但是答案A改写成命题形式为（命题4）： If the animal is a warm-blood animal, then its body temperature can not be easily controlled in the laboratory.
还有就是，如果原文是说Cold-blooded animals were used to test this hypothesis because their body temperature can be more easily controlled in the laboratory.那么似乎好理解一些。因为用了比较级，一定是和领域里的其他类别相比较而得出的。和warm-blood相对应的就只有cold-blood了，那么就可以得出答案A了。 作者: gemj 时间: 2003-11-13 04:16
这就是ETS惯用的“强对比，互取非”的思路。很常考。其实深究起来并无什么道理： 你是女人，我是男人。（强对比） 你是女人，所以你要吃饭。