so he stopped the car at once.A. Seeing a boy lying on the roadB. On seeing a boy sittin

问题补充：

, so he stopped the car at once.

A. Seeing a boy lying on the road

B. On seeing a boy sitting on the road

C. The driver had seen a boy standing on the road

D. The minute the driver saw a boy seated on the road

答案：

A. Seeing a boy lying on the road

B. On seeing a boy sitting on the road

(答案→)C. The driver had seen a boy standing on the road

D. The minute the driver saw a boy seated on the road

解析：考查状语从句，句意：这名司机看到一个男孩站在在公路上，因此他立刻停下来。这是一个原因状语从句，后面已经有了so，前一个分句不能出现because，所以选C。