The research requires more money than has been put in.

问题描述:

The research requires more money than has been put in.
这里为甚麽要用"has been put in"?

首先是MONEY肯定是被投入的.再有就是过去已经完成的动作了~!助动词have的用法 1)have+been +过去分词,构成完成式被动语态,例如:English has been taught in China for many years.(中国教英语已经多年.) 2)现在完...