The correct answer is a combination of an increase in pressure, an increase in temperature, and exposure to reactive chemical fluids.
Metamorphism of a rock can result from a combination of factors, including:
Increase in Pressure: High pressure can lead to the recrystallization of minerals in a rock, causing it to undergo metamorphism.
Increase in Temperature: Elevated temperatures can cause the minerals in a rock to recrystallize or transform into new mineral phases, resulting in metamorphism.
Exposure to Reactive Chemical Fluids: Interaction with chemically reactive fluids, such as hydrothermal fluids or metamorphic fluids, can cause mineral reactions and changes in the rock's composition, contributing to metamorphism.
Therefore, the correct answer is a combination of an increase in pressure, an increase in temperature, and exposure to reactive chemical fluids.