Answer:
A. heat; pressure
Explanation:
Metamorphic rocks are formed from preexisting rocks. The parents rocks due to temperature(heat) and pressure forms a different kind of rock with different mineral composition from the parent rocks. The change usually occur in the interior of the earth. The changes that accompany the rocks are new texture or new mineral assemblage or even both. The transformation of this rocks takes place in the solid state. This means the rocks never melts. The parents rocks are deeply buried but the heat changes are not adequate enough to melt the rocks. Therefore the heat and pressure changes alters mainly the mineral configuration and texture of the rock.
Example of metamorphic rocks is marble. Marble is formed when limestone is metamorphosed .The marble may be different mineralogically or texturally from the parents rocks. Metamorphism generally, involves changes to rocks that take place in the earth interior where heat and pressure increases.
