As I walked the countryyards I noticed how the peasants devoted hours to cleaning it.A. a

问题补充：

As I walked the countryyards, I noticed how the peasants devoted hours to cleaning it.

A. across

B. down

C. through

D. along

答案：

A. across

B. down

(答案→)C. through

D. along

解析：考查介词和动词的搭配。through从空间里穿过；across从物体的表面过去.。