Every possible means ________ to prevent
问题:
Every possible means ________ to prevent the air pollution, but the sky is still not clear. [ ]
A. has been used
B. are used
C. is used
D. have been used
Every possible means ________ to prevent the air pollution, but the sky is still not clear. [ ]
A. has been used
B. are used
C. is used
D. have been used