Which best characterizes a crystal? a number of high speed particles moving randomly a dense substance that is hard and incompressible a high-energy state of matter made up of a swirling, ionized gas a loose association of particles moving past one another mark this and return

The answer is a dense substance that is hard and incompressible.

A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions.

Hoped I helped!

The rocks expand when there hot/warm  and contract when they are cold.