Select the one substance that is not a rock.

 - Diorite is a solid. It is not made by living things.
 - A peach pit is made by a living thing. It is not a pure substance.
 - Granite is a solid. It is not a pure substance.
Compare the properties of each substance to the properties of rocks. Select the substance whose properties do not match those of rocks.
Granite is a rock.
A peach pit is made by a living thing. But rocks are not made by living things.
So, a peach pit is not a rock.
Diorite is a rock.