这种问题只能我来解答啦~ 其实这个是一个我们的推理障碍。GMAT中，这是一类论证的有一个问题是中间因素问题哦。 比方说这个，题目问的是削弱，我想你可能认为这个是加强。但是咱们来想想，如果是苹果中的某种元素导致的癌症几率的减少，其实我是不用吃苹果的，直接吃这种元素就好了。这样，苹果可以防癌这个事实就是不能成立。
Apple is rich in vitamins and is very beneficial to human health. Recently, an investigation shows that people who eat more than three apples a day have a lower risk of suffering from cancer than people who do not. Therefore, apple can help people to avoid suffering from cancer.
Which of the following, if true, most seriously undermines the argument?
A. Among the people who already suffered from cancer, those who eat apple suffer from more serious cancer than those who do not.
B. As for people who eat six apples a day, the risk of suffering from cancer is much lower than people who eat three a day.
C. Apple has some trace elements that can help people get away from cancer.
D. Apple is not a good kind of fruit for regular eating because it needs much pesticide to maintain growth.
E. Some cancer can seldom be reliably identified.
-- by 会员 majormingzhao (2012/9/20 4:17:09)
如果说有：“苹果--->苹果中的元素---->防癌” 逻辑上我们是一定不能认为：“苹果---> 防癌”的 Hope that helps~