What conditions are necessary for the formation of thunderstorms?

The formation of thunderstorms is primarily influenced by certain atmospheric conditions, which are accurately described in the chosen option. High humidity is essential as it provides the necessary moisture that fuels the development of thunderstorms. When warm, moist air rises, it cools and condenses to form clouds.

Additionally, a lifting force is crucial for initiating this upward movement of air. This lifting can come from various sources, such as geographical features, front boundaries, or the heat of the Earth's surface.

Unstable conditions are also necessary; this refers to a situation where warmer air is located near the surface, while cooler air is found above it. When this warmer air rises, it can lead to explosive vertical development of clouds, which is characteristic of thunderstorms. The combination of high humidity, the presence of a lifting mechanism, and instability leads to the rapid development of thunderstorms, making this option the correct answer.