As a Cold Front Moves into a Warm Air Mass

Multiple Choice

As a cold front moves into a warm air mass

A) there is a substantial horizontal pressure gradient at heights of a kilometer or more above the surface of the two air masses.
B) the cold front has a smaller vertical pressure gradient than does the warm air.
C) the cold front slopes backward at a ratio of between 1:5 and 1:20.
D) the warm air subsides and is overrun by the cold front.