As along the river bank she was singing a pop song.A. walkingB. walkedC. to walkD. walk

问题补充：

As along the river bank, she was singing a pop song.

A. walking

B. walked

C. to walk

D. walk

答案：

(答案→)A. walking

B. walked

C. to walk

D. walk

解析：考查连词加非谓语动词结构。Walk和逻辑主语she之间是主谓关系，且表示walk

和之间谓语动词的动作同时发生，所以用walking表主动和正在进行。选A。