题目

He looked around and caught a man _____ his hand into the pocket of a passenger. A. put            B. to be put           C. to put       D. putting 答案：D 解析: catch sb doing sth表示发觉或当场捉住 sb在做一件事情。 种子萌发的环境条件有适宜的         、一定的        、充足的         。