The following is a schematic diagram of air pressure changes before and after different weather systems. Among the four curves in the figure, the curves representing the change of air pressure before and after the cold front pass are: (

This topic investigates the weather changes under the influence of weather system. Before the cold front crossed the border, the local area was controlled by the warm air mass, so the air pressure was low; After the cold front crossed the border, the cold air mass replaced the original warm air mass, so the air pressure increased, so the C curve was correct.