Answer:
Regional metamorphism
Step-by-step explanation:
(all definitions below are NOT my own definitions, but burrowed from trustworthy informational sites)
It is not Sediment Layering because Sediment Layering is sedimentary rocks layers are piled one on top of the other.
It is not Cooling of Magman because Cooling of Magman is elements within the magma combine and crystalize into minerals that form an igneous rock.
It is not Contact Metamorphism because Contact Metamorphism is metamorphism due to contact with or proximity to an igneous intrusion.
It IS regional metamorphism because it is metamorphism affecting rocks over an extensive area as a result of the large-scale action of heat and pressure.
