The vacuum tube,invented near the beginn

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问题 The vacuum tube,invented near the beginning of our century,gave us the use of radio waves,an energy source never before（）,and later opened the road for television.A.was capturedB.capturedC.capturingD.has been captured

选项 A.was captured
B.captured
C.capturing
D.has been captured

答案 B

解析该题考查独立主格结构。其中该句主干为The vacuum tube gave us the use of...the road for television。而energy source与capture间是被动关系,排除C选项.另外an energy source是对其前radio waves做进一步解释，可见“an energy source never before”不是一个句子，而是一成分，故答案为B。

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本试题收录于：英语一研究生题库研究生入学分类