问题
选择题
You ________ knock at the door. Just come in. [ ]
A. don't have to
B. can't
C. mustn't
D. couldn't
答案
答案：A
搜题请搜索小程序“爱下问搜题”
You ________ knock at the door. Just come in. [ ]
A. don't have to
B. can't
C. mustn't
D. couldn't
答案：A