Correct Option: C

Metamorphic rocks are rocks that have “morphed” into another kind of rock. These rocks were once igneous or sedimentary rocks. How do sedimentary and igneous rocks change? The rocks are under tons and tons of pressure, which fosters heat build-up, and this causes them to change. If you exam metamorphic rock samples closely, you’ll discover how flattened some of the grains in the rock are.