You are presented with the question "What type of energy is produced the most worldwide?" and the following answer choices: 
- photons
 - food
 - chemicals
 - our star
 - Light
 - Heating
 - waves
 - sound

Now knowing that energy is used for heating a building by a heating system and energy used for heating is the single most commonly used form of energy worldwide, choose the best answer.


 

      Heating   