a) Slow cooling of magma at considerable depth
b) Quick cooling of magma at a shallow depth
c) Rapid cooling of magma at Earth’s surface
d) Rapid cooling of magma at a shallow depth

Answer: b
Explanation: Plutonic rocks are formed by slow cooling of magma at considerable depth. Volcanic rocks are formed near the surface of Earth by rapid cooling of magma. Hypabyssal rocks are formed at a quick rate of cooling of magma at considerably shallow depths.