请教各位一道老题，伤。。。

kuuiytt

In a political system with only two major parties, the entrance of a third-party candidate into an election race damages the chances of only one of the two major candidates. The third-party candidate always attracts some of the voters who might otherwise have voted for one of the two major candidates, but not voters who support the other candidate. Since a third-party candidacy affects the two major candidates unequally, for reasons neither of them has any control over, the practice is unfair and should not be allowed. If the factual information in the passage above is true, which of the following can be most reliably inferred from it? (A) If the political platform of the third party is a compromise position between that of the two major parties, the third party will draw its voters equally from the two major parties. (B) If, before the emergence of a third party, voters were divided equally between the two major parties, neither of the major parties is likely to capture much more than one-half of the vote. (C) A third-party candidate will not capture the votes of new voters who have never voted for candidates of either of the two major parties. (D) The political stance of a third party will be more radical than that of either of the two major parties. (E) The founders of a third party are likely to be a coalition consisting of former leaders of the two major parties.

答案为B，至今未想出原因~虽然觉得其他也不对

mary1

题干说，第三的party只能从支持这两个party的选民中吸引选票，而不能拉到支持其他的选民的选票。

那么B说，如果在第三个party出现之前，所有的选民被那两个party平均分，也就是一个party有1/2的选民。那么如果第三party出现后，分别或至少从一个party中拉走了一部分选票，那么要不就是那两个party的选民都少于1/2，要不就是至少一个少于1/2。所以正如B最后一句所说，这两个party没有一个能吸引多于1/2的选票。

这像是一个算术题，不知这样说明不明白，请指教！