[求助]请教大全118（987版）

118.  Art museums do not usually think of their collections as capital or consider the interest income that would be generated if a portion of the capital would have been invested in another form.

(A) be generated if a portion of the capital would have been

(B) have been generated if a portion of the capital would have been

(C) be generated if a portion of the capital were   

(D) be generated if a portion of the capital was

(D) be generated if a portion of the capital was

(E) be generated if a portion of the capital had been

答案为C，不明白后面为什么用were

为什么用复数？

长进了, 谢谢

THANKS