Question

Betty ________ fake watches when the police came．

1. A.
   sells
2. B.
   is selling
3. C.
   was selling
4. D.
   has sold

Answer 1

C
因为本句时间状语是“when…”是“当……的时候”，要用过去进行时才最恰当，只有“was selling”是过去进行时，所以正确答案是C．