Several students were working _____the difficult math problem after class. [ ]A. in B. to C. offD. o

题目简介

Several students were working _____the difficult math problem after class. [ ]A. in B. to C. offD. o

题目详情

Several students were working _____the difficult math problem after class.       
[     ]
A. in        
B. to    
C. off        
D. on
题型:单选题难度:中档来源:同步题

答案

D

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