Which of the following factors contributes to the formation of a cold front?

The formation of a cold front is primarily characterized by the movement of a mass of cold, dense air pushing into an area occupied by warmer air. This interaction is crucial because the cold air, being heavier, wedges underneath the lighter warm air. As this cold air advances, it forces the warm air to rise rapidly. This upward movement can lead to the development of clouds, precipitation, and even stormy weather, typical of the cold front scenario.

In contrast, the other factors listed do not directly contribute to the formation of a cold front. For instance, warm, moist air rising over colder air describes the process involved in warm fronts rather than cold fronts. Heat exchange between land and sea relates more to variations in temperature and pressure systems that can influence weather patterns, but it does not constitute the fundamental mechanism of a cold front itself. Stagnation of high-pressure systems typically leads to calm, stable weather conditions, which is also not aligned with the dynamic nature of cold front formation.