You are presented with the question "What does cold air replacing warm air cause?" and the following answer choices: 
- Greenhouse gases
 - Pollution
 - Dehydration
 - thunderstorms
 - steady barometer readings
 - hypothyroidism
 - constant air pressure
 - stagnant air temperature

Now knowing that cold fronts cause thunderstorms as they pass by and if cold air replaces warm air, it is called a cold front, choose the best answer.


 

    thunderstorms     