Fact 1: Coal is used for generating heat by burning.

Fact 2: Coal forms from dead plants, compacted.

Given the two facts above, answer the question "What is used for generating heat by burning?" with the following options: 
- compacted dead plants
 - basic building blocks of life
 - deoxyribonucleic acid
 - igniting fuel and oxidiser
 - hard plastics
 - soft styrofoam
 - Sulfur dioxide
 - thin metal sheets


 

 compacted dead plants        