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 candidate 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 divider equally between the 2 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 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 。。。。
key is B, but i don't know why. | 
