问题
选择题
7、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
答案:C
7、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