Gneiss, a rock found in the Teton Range, is which type of rock?

A Sedimentary
B Igneous
C Metamorphic

Metamorphic rocks are formed when existing rock is subject to heat, pressure or chemically active fluids over long periods of time. Metamorphism causes changes in mineral composition, structure and texture. Other metamorphic rocks include slate, marble and schist.

The correct answer is Metamorphic.