Question

What ______ you ______ when you father came back?

1. A.
   did, do
2. B.
   are, doing
3. C.
   were, doing
4. D.
   do, do

Answer 1

C
解析：
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。