◎ 题干
— When did the computer crash?
— This morning, while I ________ the reading materials downloaded from some websites.
[     ]
A. have sorted  
B. was sorting
C. am sorting  
D. had sorted
◎ 答案
查看答案
◎ 解析
查看解析
◎ 知识点
    根据魔方格专家分析,试题“— When did the computer crash?— This morning, while I ________ the reading materials downloaded from some websites.[ ]A. have sortedB. was sortingC. am sort…”主要考查了你对  【过去进行时】  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。