应选哪一个?

sseexx

有这样一道选择题：

(1)Fathers ______ in children's lives.
A. play big parts B. play a big part
应选哪一个? 我还见过这样一句：
(2)Geographic location and family tradition play important parts in forming dietary habits.

weicf

A吧！主语本来就是复数，后面的children也是应用了复数形式，所以用A应该是没错的。