单项选择题

It was not until 1920 ______ regular radio broadcasts began.

A．when
B．which
C．that
D．since
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单项选择题
I first met Lisa three years ago when we ______ at a radio station together.
A．have worked
B．had been working
C．were working
D．had worked
单项选择题
All the leading newspapers ______ the trade talks between China and the United States.
A．reported
B．printed published
C．announced
D．published
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