问题
选择题
What ______ you ______ when you father came back?
A．did, do
B．are, doing
C．were, doing
D．do, do
答案
答案：C
考查固定结构。Be doing…when…某人正在做某事。。。这时。。。；根据when you father came back指的是过去，所以用过去进行时，选C。
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