Fact 1: Burning wood is used to produce heat.

Fact 2: Interior woods are birch, spruce and pine.

Given the two facts above, answer the question "What is burned to produce heat?" with the following options: 
- Oak
 - Gold
 - Spruce
 - cellulose
 - Conifers
 - bamboo
 - Plastic
 - Aluminum


 

   Spruce      