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31．We believe scientists will a way to solve the problem of air pollution．A．catch up with B．come up with C．put off D．set off 【查看更多】

 

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We believe scientists will ________ a way to solve the problem of air pollution．


  1. A.
    set off
  2. B.
    put off
  3. C.
    come up with
  4. D.
    catch up with

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