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Scientistsinterestedintheproblem()atitforyear.A.hasbeenworkingB.hasworkedC.havebeenworkingD.working
题目详情
Scientists interested in the problem ( )at it for year.A.has been working B.has worked C.have been working D.working
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答案和解析
选C.
句子的主干是Scientists have been working on it.
interested in the problem做scientists的定语.
for years 表示时间段前面要要用完成时
此句子表示到说话这一刻起这个动作还在进行,所以用现在完成进行时.
如果到说话时已经结束则要用现在完成时.
句子的主干是Scientists have been working on it.
interested in the problem做scientists的定语.
for years 表示时间段前面要要用完成时
此句子表示到说话这一刻起这个动作还在进行,所以用现在完成进行时.
如果到说话时已经结束则要用现在完成时.
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