at the gate of the theater, Susan found the ticket for the play was left at home.
A. To arrive
B. On arriving
C. As arriving
D. While arrived
网友回答
A. To arrive
(答案→)B. On arriving
C. As arriving
D. While arrived
解析：句意：苏珊一到剧院的门口，就发现电影票被忘在家里了。On+名词/动名词=as soon as“一......就....”故选B。