◎ 题干
You ________ knock at the door. Just come in.  
[     ]
A. don't have to        
B. can't  
C. mustn't            
D. couldn't
◎ 答案
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◎ 解析
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◎ 知识点
    根据魔方格专家分析,试题“You ________ knock at the door. Just come in. [ ]A. don't have toB. can't C. mustn'tD. couldn't…”主要考查了你对  【情态动词】  等知识点的理解和应用能力。关于这些知识点的“档案”,你可以点击相应的链接进行查看和学习。