Fact 1: Heat and pressure change the remains of prehistoric living things into natural gas.

Fact 2: Heat and pressure cause a rock to metamorphize.

Given the two facts above, answer the question "What can change the remains of prehistoric living things into natural gas?" with the following options: 
- rock metamorphizing
 - a hydraulic system
 - Time and energy
 - the ground shaking
 - Temperature
 - one celled organisms
 - chemical reaction
 - flow of electrons


 

 rock metamorphizing        