It was 1920 regular radio broadcasts began. A. whileB. whenC. thatD. since

发布时间：2020-08-16 19:36:28

It was 1920      regular radio broadcasts began.
A. while
B. when
C. that
D. since

网友回答

A. while
(答案→)B. when
C. that
D. since
解析：考查定语从句。when 指先行词1920 。
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