In the following four pictures, () A.B.C.D correctly represents the cold front weather.

A, from the arrows of cold and warm air in the figure, it can be judged that it is a cold front, so it is correct;

B, the density of cold air mass is large, below the front, which does not meet the meaning of the question;

C, the density of cold air mass is large, below the front, which does not meet the meaning of the question;

D, the cold front is the front where the cold air mass moves to the warm air mass, which does not conform to the meaning of the question.

So choose: a