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-Look! How dirty the river is! -But it clear before a factory was set up nearby. A. used to be B. will be C. has been D. is 【查看更多】

 

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－Look! How dirty the river is!

－But it ________ clear before a factory was set up nearby.

A. used to be  B. will be　　    C. has been　　 D. is 

 

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