They preferred to school a bus.A. to walk takeB. walking to takingC. to walk take D.

问题补充：

They preferred to school a bus.

A. to walk, take

B. walking, to taking

C. to walk, take

D. walk, to take

答案：

A. to walk, take

(答案→)B. walking, to taking

C. to walk, take

D. walk, to take

解析：prefer A to B表示与B相比更喜欢A，主语A和B结构一定要相同，动名词表示抽象动作，结合语境，可知选B。