The thief took off his shoes when he slipped into the house in order to steal something .
A. unnotice
B. unnoticed
C. unnoticing
D. to unnotice
网友回答
A. unnotice
(答案→)B. unnoticed
C. unnoticing
D. to unnotice
解析：考查非谓语动词：句意：小偷溜进房间的时候脱下鞋子为了在不被注意的情况下偷东西。因为the thief和unnotice是被动关系，这里是过去分词做状语，所以选B。