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Every possible means ______ to prevent the air pollution, but the sky is still not clear.

A. is used        B. are used           C. has been used   D. have been used

Every possible means ______ to prevent the air pollution, but the sky is still not clear.

A. is used    B. are used    C. has been used     D. have been used

Every possible means ___ to prevent the air pollution, but the sky is still not clear．

Every possible means _____ to prevent the air pollution, but the sky is still not clear.

A. is used B. are used C. has been used D. have been used

 Every possible means ___ to prevent the air pollution, but the sky is still not clear．

         A．is used       B．a(chǎn)re used     C．has been used                  D．have been used

 Every possible means _______to prevent the air pollution, but the sky is still not clear.

A. are being used   B. have been used   C. has been used  D. had been used

Every possible means ________ to prevent the air pollution, but the sky is still not clear.

A. is used     B. are used     C. has been used     D. have been used

7、Every possible means ______ to prevent the air pollution, but the sky is still not clear.

Every possible means _______to prevent the air pollution, but the sky is still not clear.

A. are being used     B. have been used        C. has been used      D. had been used

Every possible means ______ to prevent the air pollution, but the sky is still not clear.

A. is used　 B. are used　 C. has been used　　 D. have been used