Fact 1: Awindmill converts wind energy into electricity primarily by using mechanical energy.

Fact 2: Mechanical energy is the energy of moving objects.

Given the two facts above, answer the question "what does a windmill primarily use to convert wind energy into electricty?" with the following options: 
- matter vibrating
 - stored energy
 - solar power
 - batteries
 - Movement of an air mass
 - heat is produced
 - energy of moving objects
 - Something to move


 

       energy of moving objects  