◎ 题干
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
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◎ 解析
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◎ 知识点
    根据n多题专家分析,试题“It was not until the beginning of the twentieth century________to explore space.[ ]A.did man begin B.when man beganC.that man beganD.then man began…”主要考查了你对  【同位语从句】  等知识点的理解和应用能力。关于这些知识点的“档案”,你可以点击相应的链接进行查看和学习。