What's the difference between problem and trouble?

A problem usually has some sort of solution. 

Problem is something that need to be solved and trouble is a feelings that you get when something bad happens.

The correct answer in this question  is option c. people in mountainous areas tend to be more isolated from other populations. this is the reason why their local languages do not spread. farming is their  one way of living among the highlanders.

Ithink it is a. im not all that sure though.