You are presented with the question "What are the lithified remains of plants used for?" and the following answer choices: 
- heat production
 - generating heat by burning
 - harvesting crops
 - damming rivers
 - food and shelter
 - heat is produced
 - A transportation fuel
 - planting seeds

Now knowing that coal is used for generating heat by burning and coal and lignite are the lithified remains of plants, choose the best answer.


 

  generating heat by burning       