It is known to all that light travels in straight lines.When the plane is to take off has not been announced . 是什么从句及句子成分

分类: 作业答案 • 2021-12-20 03:12:40

问题描述：

It is known to all that light travels in straight lines.
When the plane is to take off has not been announced . 是什么从句及句子成分

答