It was foolish of you to take a taxi you could easily walk there in five minutes.A. while

问题补充：

It was foolish of you to take a taxi you could easily walk there in five minutes.

A. while

B. when

C. since

D. before

答案：

A. while

(答案→)B. when

C. since

D. before

解析：考查状语从句引导词. A.当……时候，强调主从动作同时发生 B. 当……时候 C. 自从……以来 D.在……以前。根据题意，当你能轻松的在五分钟内走到那儿的时候，打出租车简直太蠢了。故选B。