be quick和be quickly的区别是什么啊?

问题描述:

be quick和be quickly的区别是什么啊?
有没有be quick这个用法?
He was _______the teacher's questions.
A.quickly to undersand B.quick to understand
C.quickly understood D.quick understanding

个人觉得应该选B
be quick to do somthing
如果选c,was understood就是被动语态了.