Given a scientific question, generate a correct answer to it.

Example Input: What structures are located on roof of the nasopharynx and on each side of the pharynx?
Example Output: tonsils

Example Input: What is the term for a substance that increases the rate of a chemical reaction but is not changed or used up in the reaction?
Example Output: a catalyst

Example Input: The way a mineral cleaves or fractures depends on what part of the mineral?
Example Output:
the crystal structure