I am not sure ( )there are living things on other plants or not.Even scientists are not sure.

分类: 作业答案 • 2021-12-31 13:25:14

问题描述：

I am not sure ( )there are living things on other plants or not.Even scientists are not sure.
A.if B.that C.whether D.where
为什么不可以选A有什么结构吗?

答

or not不能和if连用,只能用whether