◎ 题干
When you want to go into the room, you should _____ the door.        
[     ]
A. knock on
B. knocking on
C. knocks at
D. to knock at
◎ 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“When you want to go into the room, you should _____ the door.[ ]A. knock onB. knocking on C. knocks at D. to knock at…”主要考查了你对  【动词短语】  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。