How does fast-moving cold air create thunderstorms when combined with warm air?

When a cold front meets a warm front, the two cannot mix because of the difference in temperatures and densities. The result is that the warm air, being lighter, will usually be pushed atop the colder air. The air cools as it rises. As this happens, the water vapor in it condenses, forming clouds.

Answer(a); // soil salinization and waterlogging;

Answer steam fog;