Select the one substance that is not a rock.
Trachyte is a solid. It is not a pure substance. A skull is made by a living thing. It is a solid. Syenite is not made by living things. It is not a pure substance.
Rocks are made of minerals. Here are some properties of rocks:
They are solid.
They are formed in nature.
They are not made by living things.
They are not pure substances.
Compare the properties of each substance to the properties of rocks. Select the substance whose properties do not match those of rocks.
A skull is made by a living thing. But rocks are not made by living things.
So, a skull is not a rock.
Syenite is a rock.
Trachyte is a rock.