Answer the following question given this paragraph: 

Metamorphism. This long word means “to change form. “ A rock undergoes metamorphism if it is exposed to extreme heat and pressure within the crust. With metamorphism, the rock does not melt all the way. The rock changes due to heat and pressure. A metamorphic rock may have a new mineral composition and/or texture.


Q: What is a rock exposed to if it's undergoing metamorphism?


A:
heat and pressure