It was not until 1920regular radio broadcast began.A. whileB. whichC. thatD. since

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

A. whileB. which(答案→)C. thatD. since解析：众所周知，当时间状语由until/till引出时，如果谓语动词为非延续性动词，则要用否定式，表示“直到……才……”。本句的正常结构应为：Regular radio broadcast didn’t begin until 1920.如果强调本句的时间状语，则要把not和until...一起放在句首，可以构成：Not until 1920 did regular radio broadcast begin.（注意表示否定意义的副词位于句首，要倒装），如果使用强调结构，则可构成：It was not until 1920 that regular radio broadcast began.

和我的回答一样，看来我也对了