Final answer:
Rock composition is not an agent of metamorphic change; rather, it is the characteristic of the parent rock. The actual agents of metamorphism include stress, temperature, pressure, and chemically reactive fluids.
Step-by-step explanation:
The question asks which of the following is not an agent of metamorphic change: stress, temperature, pressure, rock composition, or strain. In the context of geology, the agents that contribute to the formation of metamorphic rocks include temperature, pressure, and the presence of chemically reactive fluids. These agents facilitate the recrystallization and chemical alteration of minerals within the rock, leading to a metamorphic change. Rock composition is crucial in determining what type of metamorphic rock will result, but it is not an agent of change; it defines the characteristics of the protolith (parent rock). Therefore, rock composition is not an agent of metamorphic change, which is brought about by a combination of stress, temperature, pressure, and sometimes chemically reactive fluids.