我昨天给你打电话的时候，你在干嘛？．

Question

我昨天给你打电话的时候，你在干嘛？
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Answer 1

答案：What were you doing when I called you yesterday？
这里用when引导的时间状语从句来表达，从句我昨天给你打电话的时候，表达的是昨天yesterday的事情用一般过去时，主语I，打电话call sb，故 when I called you yesterday，主句表达的是过去正在进行的动作用过去进行时was/were+doing，主语you，故were，这里是特殊疑问句，what什么，作为疑问词，后加一般疑问句语序，were提前，故答案是What were you doing when I called you yesterday？