to their surprise,they found the lecture given by the famous professor easy ___.

题目

to their surprise,they found the lecture given by the famous professor easy ___.
A to be understood B to understand C understanding D understood
为什么?

答案

B
这里不定式直接表示被动的意思,不需要再用被动形式.
这种结构的名称叫什么我忘记了,但是很常见,比如：
English is easy to learn.就不会说easy to be learnt.