题目

While the boy ______ down the street, the UFO _____ .A．was walking; was landingB．walked; landedC．was walking; landedD．walked; was landing 答案：C解析:本题是考查while 引导的从句，其中主句为短暂性动词，从句为延续性动词，且主句的动作发生在从句的动作中，故选C

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