The thief took off his shoes when he slipped into the house in order to steal something .A

问题补充：

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

答案：

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。