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

Fact 2: Windmills tap into the energy of the wind using sails or vanes.

Given the two facts above, answer the question "What do windmills use to convert energy?" with the following options: 
- Heat
 - fibers
 - copper
 - cycles
 - SO2
 - Vanes
 - calcite
 - Lift


 

      Vanes   