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

    [　　]

    A．discovered

    B．have discovered

    C．had been discovered

    D．have been discovered

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