Answer:
Option C:
The magma's cooling rate determines the size of crystals that are formed.
Explanation:
Once magma erupts from a volcano to the surface of the earth, it begins to cool because of the relatively cooler temperatures at the surface of the earth.
The magma usually cools down to form igneous rocks on the surface of the earth. The rate at which the magma cools down determines the size of the rock crystals that are formed.
If the magma cools slowly, there is enough time for crystal growth within the rock particles. This gives rise to larger rock crystals.
If the magma cools rapidly, there is little time for crystal growth. This leads to the presence of smaller rock crystals.
