Fact 1: An incandescent light bulb converts electricity into light by sending electricity through a filament.

Fact 2: Incandescent bulbs produce more heat than light.

Given the two facts above, answer the question "What do incandescent bulbs produce as they create electricity?" with the following options: 
- energy
 - heat
 - fuel
 - smoke
 - gas
 - fields
 - copper
 - waves


 

  heat       