问题
It was not until the beginning of the twentieth century________to explore space.
A:did man begin
B:when man began
C:that man began
D:then man began
B:when man began
C:that man began
D:then man began
正确答案是：
同类题型
You should the new words that you don’t know how to spell.
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I think collecting things is good for health.—Yes, I quite ______ you. [ ]