Question

—How long _______it _______ you to work out such a difficult problem?
—About thirty minutes

1. A.
   did… take
2. B.
   does… take
3. C.
   did…cost

Answer 1

A
考查时态和词义辨析。“解出这道难题花费了你多长时间啊？”“差不多30分钟。”take后加时间；cost后加钱。根据句意可知，应该用过去时。故选A。