帮我看一个非谓语动词选择题

题目

帮我看一个非谓语动词选择题
6.The professor could hardly find sufficient grounds _____ his arguments in favor of the new theory.
A.to be based on B.to base on C.which to base on
D.on which to base
D 为什么不能A呢?

答案

6. The professor could hardly find sufficient grounds _____ his arguments in favor of the new theory. A. to be based on B. to base on C. which to base on D. on which to base答案：D 为什么...