The thief was caught his hand into the pocket of a passenger.
A. to be putting
B. to put
C. putting
D. put
网友回答
A. to be putting
B. to put
(答案→)C. putting
D. put
解析：考查固定搭配。固定搭配catch sb doing sth抓住某人正在做某事；本句是其被动语态sb be caught doing 某人做某事的时候被抓住。句意：当这个小偷把手伸进乘客的口袋的时候，当场被抓住。故C正确。