the main nutrient in all foods a type of grain found in cereals a natural substance that makes up rocks the decomposed plant matter found in soil
I gave my students this multiple choice question: Which of the following best describes a mineral?

Only one answer is correct among these 4 choices:
- the main nutrient in all foods
- a type of grain found in cereals
- a natural substance that makes up rocks
- the decomposed plant matter found in soil

Could you tell me which one is correct?

a natural substance that makes up rocks