We have heard him sing改为被动语态.He ____ ____ ____ ____ ____ by us.

问题描述:

We have heard him sing改为被动语态.He ____ ____ ____ ____ ____ by us.
hear 后面不是不可以加to do 不定式吗,请注意要填五个空!

has been heard to sing 被动语态时"to do"是要还原的