XDF补充教材的逻辑题（请教）

In a political system with only two major parties, the entrance of a third-party candidate into an election race damage the chances of only one of two major candidates. The third-party candate 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?
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 candate will not capture the votes of new voters who have never voted for candidates of either the two major parties.
答案是B，我怎么觉得是C呀？