问题
选择题
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
答案
答案：C
C mean单数复数一个形式。在本题中代表单数。
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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
答案：C
C mean单数复数一个形式。在本题中代表单数。