Fact 1: Energy is used for heating a building by a heating system.

Fact 2: Energy used for heating is the single most commonly used form of energy worldwide.

Given the two facts above, answer the question "What type of energy is produced the most worldwide?" with the following options: 
- photons
 - food
 - chemicals
 - our star
 - Light
 - Heating
 - waves
 - sound


 

      Heating   