It is still unknown caused the accident last Saturday.A. thatB. whenC. whatD. how

发布时间：2020-08-16 22:06:08

It is still unknown     caused the accident last Saturday.
A. that
B. when
C. what
D. how

网友回答

A. that
B. when
(答案→)C. what
D. how
解析：本题考查主语从句。It是形式主语，     caused the accident last Saturday是主语从句，引导词要做caused 的主语， 所以用what。
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