The air in big cities very dirty by factories.A. are often madeB. is often made C. have of

发布时间：2020-08-16 07:30:27

The air in big cities     very dirty by factories.
A. are often made
B. is often made
C. have often made
D. has often made

网友回答

A. are often made
(答案→)B. is often made
C. have often made
D. has often made
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