The policeman looked around and caught a manhis hand into the pocket of a passenger.A. put

问题补充：

The policeman looked around and caught a manhis hand into the pocket of a passenger.

A. put

B. to be putting

C. to put

D. putting

答案：

A. put

B. to be putting

C. to put

(答案→)D. putting

解析：考察固定搭配。固定搭配catch sb doing sth抓住某人正在做某事；句中的动词putting和catch是同时发生的事情，故使用现在分词的形式来表示。句意：那个警察环顾四周，当场抓住一个把手伸进乘客口袋的人。故D正确。