---- What happened to you?
---- I in the street when someone patted me on the shoulder, which frightened me.
A. was about to walk
B. was walking
C. had walked
D. walk
网友回答
A. was about to walk
(答案→)B. was walking
C. had walked
D. walk
解析：句意：你发生什么事情了？--我正走在街上，这时有人拍我的肩膀，这使我很害怕。这里用了过去进行时，表示when someone patted me on the shoulder这个时候，真正发生的事情，所以选B。