Question

【题目】It is known ____________ light travels faster than sound.

A. as B. that C. what D. which

Answer 1

【答案】B

【解析】此句中It是形式主语，真正的主语是后面的that从句，从句中不缺成分，故用了that。It is known that…表示＂众所周知……＂。