the two-party election is so fierce that --- side may determine the difference between victory

题目

the two-party election is so fierce that --- side may determine the difference between victory
the two-party election is so fierce that ----- side may determine the difference between victory and defeat for a few votes.
A.either B.each C.both
带上解析.

答案

A .
析：
首先,side是单数形式,排除掉both.
其次,根据句意,只能有一方有决定权.either（两者其一）：要么this one,要么the other one.
而each是“每一个”的意思,相当于“都”.根据句意排除.