Fact 1: Extreme heat and pressure change rock into metamorphic rock.

Fact 2: Most of the heat for the Earth comes from the core.

Given the two facts above, answer the question "What creates metamorphic rock?" with the following options: 
- gravity
 - calcite
 - Earth's core
 - engine
 - desire
 - a hydraulic system
 - forces
 - flow of electrons


 

   Earth's core      