When a warm air mass and cold air mass come together, like a warm front and cold front, a typical outcome is rain. What explains why rain forms in this situation?

A. The cold air causes the moisture in the warm air to condense and precipitate as rain.
B. The cold air is moving faster than the warm air, which causes rain.
C. Because the cold air is denser, it causes rain.
D. The two air masses neutralize each other, which results in clouds that produce rain.