【答案】it was not until 1920 regular

题目：
it was not until 1920()regular radio broadcast began. A:while B:which C:that D:since 答案：C:that 解析：It was not until 1920 that regular radio broadcast began. 直到1920年,才有收音机. that引导not until的从句,为：It is not until…that…句型,意思是：直到…才…