Select the one substance that is not a rock.

 - Soapstone is a solid. It is not made by living things.
 - Paper is made in a factory. It is a solid.
 - Chert 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.
Paper is made in a factory. But all rocks are formed in nature.
So, paper is not a rock.
Chert is a rock.
Soapstone is a rock.