all you had to do was think a little harder ,was后面为什么加think的原形?

问题描述:

all you had to do was think a little harder ,was后面为什么加think的原形?

为你

was 是系动词,后面的不定式短语 to think... 作表语.
当was前面出现动词do的时候,不定式符号to可以省略,此时就剩下think了.

不懂请追问,满意请采纳.谢谢!