David didn't give up ______ he had failed in the experiment four times.[ ]A. ifB. while C. thou

题目简介

David didn't give up ______ he had failed in the experiment four times.[ ]A. ifB. while C. thou

题目详情

David didn't give up ______ he had failed in the experiment four times.      
[     ]
A. if            
B. while        
C. though        
D.since
题型:单选题难度:中档来源:江苏省模拟题

答案

C

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