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11．Pollution is a serious problem．Scientists have some good ways to solve It．A．come up with B．come on C．come out D．come up 【查看更多】

 

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Pollution is a serious problem．Scientists have ________ some good ways to solve it.


  1. A.
    come up with
  2. B.
    come on
  3. C.
    come out
  4. D.
    come up

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