Cold and Warm Air Mass and Temperature in Geographical Cold and Warm Fronts

The front map given in this question is a cold front weather map, which can be obtained according to the moving direction of cold air masses. If it is warm front weather, the cold air mass will rise first and then sink. The cold air mass in this picture moves in one direction, so it is a cold front. The cold front is very strong in the cold air mass, pushing the front forward, so the front moves to the right. A is controlled by cold air mass, C is controlled by warm air mass, and B is controlled by the intersection of cold and warm air mass, so C is selected.