问题
选择题
It's polite to ________ the door before you go into the room. [ ]
A. shout at
B. knock on
C. look at
D. listen to
答案
答案：B
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It's polite to ________ the door before you go into the room. [ ]
A. shout at
B. knock on
C. look at
D. listen to
答案：B