Please help me!

A thunderstorm starts to form when water evaporates to form clouds. Which of the following best explains why thunderstorms usually form on warm days?

A. The warm air over the Earth's surface rises and pushes the clouds higher.

B. The warm air produces a high pressure system, which causes unstable conditions.

C. The water vapor in the air is warmed and this prevents it freezing.

D. The ocean and the land are heated evenly, which forces the clouds to move upwards.