—How long it you to work out such a difficult problem? —About thirty minutes. A. did… ta

问题补充：

—How long it you to work out such a difficult problem?

—About thirty minutes.

A. did… take B. does… take C. did…cost

答案：

解析：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。