Be careful your things when you are on the train.A. to B. with C. in

问题补充：

Be careful your things when you are on the train.

A. to B. with C. in

答案：

解析：to到，向；with带有，伴随；in 在里面；句意：当你坐火车时，小心你的东西。短语be careful with小心对待，故选B。