Which statement best describes metamorphic rocks?

• A. They form by crystallization from cooling magma.
• B. They form by recrystallization under heat and pressure.
• C. They originate from sediment deposition.
• D. They are always foliated.

Answer: (B)

Metamorphic rocks form when existing rocks are transformed by heat, pressure, and often fluids deep in the Earth's crust. Under these conditions, minerals recrystallize and sometimes reorient, changing the texture and mineral makeup without the rock melting. That idea—recrystallization under heat and pressure—best captures what happens during metamorphism and explains why these rocks can develop characteristic textures like foliation when directed pressure is involved.

Crystallization from cooling magma produces igneous rocks, not metamorphic ones. Sedimentary rocks arise from sediment deposition and lithification, not metamorphic transformation. And not all metamorphic rocks are foliated; some, like marble and quartzite, are nonfoliated because they form without directed stress that aligns minerals.