Select the one substance that is not a rock.
Conglomerate is not made by living things. It is not a pure substance. Marble is a solid. It is not made by living things. Steel is made by humans. 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.
Conglomerate is a rock.
Steel is made by humans. But rocks are not made by living things.
So, steel is not a rock.
Marble is a rock.