2．With the help of high technology.more and more new substances in the past years. A．disco——青夏教育精英家教网—

摘要：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

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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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