问题
选择题
The police tried _____ to break up the protest crowds. [ ]
A. in a vain
B. in vain
C. in the vain
D. for vain
答案
答案：B
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The police tried _____ to break up the protest crowds. [ ]
A. in a vain
B. in vain
C. in the vain
D. for vain
答案：B