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    2．With the help of high technology.more and more new substances in the past years. A．discovered B．have discovered C．had been discovered D．have been discovered 【查看更多】

     

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    With the help of high technology，more and more new substances ________ in the past years.（ ）

    A. discovered　　　　　　　　　 　 B. have discovered

    C. had been discovered　　　　　　　　 D. have been discovered

     

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    With the help of high technology，more and more new substances　　　　　　 in the past years.?

    A.discovered　　　　　　 B.have discovered?　　

    C.had been discovered　 D.have been discovered

     

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