有复旦大学英语系的学姐吗？

Helen_______ her former classmate when she was on the train bound for Germany.
A ran into B hit on C bumped against D rushed at
这个是题目 答案是A
我想请问：为什么不能选B ran into 和 hit on在这里有什么区别吗 ？
求分析 谢谢！！

Chances favor the prepared mind.Your hard work will eventually( )
A、pay back B、go off C、pack off D、be paid
请问 应该选哪一个？顺带分析一下原因吧！谢谢！！