depends on if you on plato or not
it cools slower in the earth meaning the crystals have more time to form than lava on the surface
the correct answer is 4) heat and pressure
metamorphic rocks arise from transformation of existing rocks types, in a process called metamorphism. during metamorphism the original rock(prolith) change into metamorphic rock by heating (150-200c) and pressure of more than 1000 bar. the original rock can be sedimentary, igneous, or existing metamorphic rock.