What is the relationship between the rate at which molten material cools and a mineral's crystals?

The faster the cooling, the larger the crystals.

The slower the cooling, the larger the crystals.

The rate at which molten material cools does not affect crystal shape.

The rate at which molten material cools does not affect crystal size.

The relationship between the rate at which material cools and mineral's crystals is:

The slower the cooling, the larger the crystals.

Explanation:

The reason behind this is the very nature of magma and its solidification. First of all, magma is supersaturated with minerals making it a very complex substance. Therefore if the magma cools quickly the different elements won't have enough time to establish enough cohesion to form large crystals. While if it has a larger amount of time making it cool slowly it will be able to form larger crystals.