问题
选择题
He looked around and caught a man __________ his hand into the pocket of a passenger.
A．put
B．to be putting
C．putting
D．to put
答案
C
题目分析：整句话的意思是：他环顾四周，偶然撞见一个男人把手放进了一位顾客的口袋里！固定句型catch sb. doing sth 偶然撞见某人在干某事~~~，这里的现在分词是做宾语补足语，强调动作的主动和进行，所以选C。