It was not until 1920 regular radio broadcasts began.A. whenB. whichC. thatD. since

发布时间：2020-08-17 15:03:37

It was not until 1920      regular radio broadcasts began.
A. when
B. which
C. that
D. since

网友回答

A. when
B. which
(答案→)C. that
D. since
解析：这是一个强调句式
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