Fact 1: Hydropower requires damming a river.

Fact 2: Another source of energy is hydropower.

Given the two facts above, answer the question "What is a source of energy?" with the following options: 
- fossil fuels
 - cooking
 - damming a river
 - sleeping
 - napping
 - Electrical energy
 - our nearest star
 - sunlight


 

   damming a river      