-Did you receive my letter?

问题描述:

-Did you receive my letter?
-I received one just as i ( )
A.set B.had set out C.was setting out D.would set out

C was/were doing 过去进行时,表示过去某时间正在做某事或那时正打算做某事.此句意思是我正打算出门时收到一封信,