A pure substance is determined by a constant composition that is definite. It includes water, methanol, and copper but not aspirin. Thus, option C is correct.
A pure substance has been constituted of the substances that are made of the invariant composition that are not subjected to transformation when undergoing chemical changes.
An atom, element, molecule, or compound can be a pure substance. Water is a pure substance as it is a compound with a definite ratio of oxygen and hydrogen.
Copper being an element is a pure substance, and similarly, methanol a type of alcohol is a pure substance when no other substance like water is added to it. Aspirin is not a pure substance as it is a homogeneous mixture made of various salts.
Therefore, option C. aspirin is not a pure substance.
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