What three elements are required for a thunderstorm to form?

The formation of a thunderstorm is dependent on specific atmospheric conditions, and the correct combination is unstable air, moisture, and lifting action. Unstable air is crucial because it allows warm air to rise rapidly, which is necessary for the development of convection currents that lead to thunderstorm formation. When the warm, moist air rises, it cools and condenses to form clouds and precipitation, leading to storm development.

Moisture is vital because it provides the necessary water vapor that, when cooled, will condense into clouds and eventually result in rainfall, sometimes accompanied by lightning and thunder.

Lifting action is the mechanism that helps push the warm air upwards. This could occur due to various factors like terrain features (like mountains), weather fronts, or converging winds that force air to rise. Without this lifting action, warm air would not have an effective outlet to rise, limiting the potential for storm development.

The other options do not encompass the essential criteria for thunderstorm formation. For example, while stable air may seem beneficial, it actually inhibits vertical movement, preventing the necessary instability for storm development. Similarly, while humidity is important, it must be coupled with unstable air and suitable lifting mechanisms to result in a thunderstorm.