We mustn't go into the teachers' office withouton the door.[ ]A. knockB. to knockC. knocki

题目简介

We mustn't go into the teachers' office withouton the door.[ ]A. knockB. to knockC. knocki

题目详情

We mustn't go into the teachers' office without              on the door.
[     ]
A. knock
B. to knock
C. knocking
D. knocked
题型:单选题难度:中档来源:同步题

答案

C

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