at the door before you enter my room, please. [ ]A. Knock B. Knocking C. Knocked
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______ at the door before you enter my room, please.[ ]A. Knock
B. Knocking
C. Knocked
D. To knock
试题答案
A
______ at the door before you enter my room, please.[ ]A. Knock
B. Knocking
C. Knocked
D. To knock
A