You are presented with the question "Uneven heating of the Earth 's surface causes a movement of what?" and the following answer choices: 
- wind
 - light
 - air
 - soil
 - sand
 - asteroids
 - cookies
 - Aves

Now knowing that uneven heating of the Earth 's surface cause wind and wind is a movement of air, and air is invisible, choose the best answer.


 

   air      