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  • 更新 2022-09-03
  • 科目 英语
  • 题型 单选题
  • 难度 中等
  • 浏览 699

With the help of high technology, more and more new substances ___in the past few years.

A.discovered B.have discovered
C.had been discovered D.have been discovered
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Withthehelpofhightechnology,mo