Question

select the correct answer. which rock has the highest metamorphic grade? a. rock formed at 500°c and 8 kilobars of pressure b. rock formed at 1,200°c and 20 kilobars of pressure c. rock formed at 400°c and 12 kilobars of pressure d. rock formed at 700°c and 10 kilobars of pressure

Explanation:

Metamorphic grade increases with higher temperature and pressure. Comparing the given temperature - pressure conditions, option B has the highest temperature ($1200^{\circ}C$) and high pressure (20 kilobars). Higher temperatures and pressures generally lead to higher - grade metamorphism.

Answer:

B. rock formed at 1,200°C and 20 kilobars of pressure