If cold air advancing on warm air can cause a thunderstorm to occur, then which situation can cause a thunderstorm?

Answer choices:
- Fog rising over a lake
 - pressure differences.
 - Earth's axis of rotation is tilted
 - Setting up lightning rods
 - Cold air advancing on cold air
 - Cold air advancing on warm air
 - Changing the angle of the sun
 - fall moving to winter

 

      Cold air advancing on warm air    