origin of the rocks. use of the rocks. size of the rocks. hardness of the rocks.
I gave my students this multiple choice question: Rocks can be classified many different ways, including as igneous, metamorphic, and sedimentary. This classification is based on the

Only one answer is correct among these 4 choices:
- origin of the rocks.
- use of the rocks.
- size of the rocks.
- hardness of the rocks.

Could you tell me which one is correct?

origin of the rocks.