题目内容
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?
答案:C
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题目内容
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?