Answer the following question given this paragraph: 

Cooling and forming crystals. Deep within the Earth, temperatures can get hot enough to melt rock. This molten material is called magma. As it cools, crystals grow, forming an igneous rock. The crystals will grow larger if the magma cools slowly, as it does if it remains deep within the Earth. If the magma cools quickly, the crystals will be very small.


Q: What is the molten material deep within the earth?

 Choices:

- volcanic mass

- crystals

- lava

- magma

A:
magma
