Answer the following question given this paragraph: 

Minerals can form various shapes. Polygons are pictured below ( Figure below ). The shapes form as the minerals are broken along their cleavage planes. Cleavage planes determine how the crystals can be cut to make smooth surfaces. People who cut gemstones follow cleavage planes. Diamonds and emeralds can be cut to make beautiful gemstones.


Q: The shapes of minerals form as they are broken along what planes?

 Choices:

- parallel planes

- sedimentary planes

- calcium planes

- cleavage planes

A:
cleavage planes
