—What's behind the door?—There must be a dog _____ behind it.[ ]A. to sit B. sitC. sitting D. t

题目简介

—What's behind the door?—There must be a dog _____ behind it.[ ]A. to sit B. sitC. sitting D. t

题目详情

—What's behind the door?
—There must be a dog _____ behind it. 
[     ]
A. to sit    
B. sit
C. sitting    
D. to sitting
题型:单选题难度:中档来源:同步题

答案

C

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