You are presented with the question "Where do fossil fuels come from?" and the following answer choices: 
- Dead prehistoric beings
 - Under water
 - basic building blocks of life
 - dead organisms
 - decaying trees
 - burning coal
 - A factory
 - Outerspace

Now knowing that heat and pressure change the remains of prehistoric living things into natural gas and natural gas is the cleanest of the fossil fuels, choose the best answer.


 

 Dead prehistoric beings        