Every possible means _______ to prevent
问题:
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