Occluded Front Structure MET
These questions are relatively easy with one trick. Firstly, the warm air will always be aloft as it is the least dense. This should reduce the possible options to two.
Now, for a warm front, remember "Y warm". If you draw a Y, this will show you where the zones are (assume the front is travelling to the left. The air at the bottom will be the coldest (this is to the right of the Y, so ahead) and the middle layer the cold air. Hence, in a warm front, the cold air is behind the coldest.
For a cold front, the situation is reversed, and the coldest air is below (behind) the cold air.