5. Most parents who are generous are good parents, but some self-centered parents are also good parents. Yet all good parents share one characteristic: they are good listeners. If all of the statements in the passage are true, which one of the following must also be true? (A) All parents who are good listeners are good parents. (B) Some parents who are good listeners are not good parent. (C) Most parents who are good listeners are generous. (D) Some parents who are good listeners are self-centered. (E) Fewer self-centered parents than generous parents are good listeners.
Please, guys, help me analyze this one. Since good parents is a subset of good listeners. In addition to D, B should be also right?
答案是D. A 不行因为逆命题不一定成立。B同样也不行，因为 同A有一点类似的地方，文章并没有证据说明All parents who are good listeners are good parents.不成立。（只是不一定成立）。所以不能说明Bmust also be true。注意must . 当然D 肯定是对的。
all good parents share one characteristic;they are good listeners. 这句话推出good parents 是good listeners的充分条件,即如果是good parents 就一定是good listeners.那么逆否命题就应该是:如果不是good listeners,就一定不是good parents.即,parents who are not good listeners are not good parents.
B 说some parents who are good listeners are not good parents 是与逆否命题相矛盾的
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发表于 2003-12-20 11:27:00
