问题
选择题
It's cold outside. You should _______ your coat. [ ]
A. put up
B. put down
C. put on
D. put out
答案
答案：C
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It's cold outside. You should _______ your coat. [ ]
A. put up
B. put down
C. put on
D. put out
答案：C
（已配平)。则符合条件的B的结构最多有(不考虑立体异构）