Final answer:
Copper is not a solution among the given options, as it is a pure element, in contrast to brass, air, and vodka, which are all examples of homogeneous mixtures or solutions.
Step-by-step explanation:
The substance from the options given that is NOT a solution is c) Copper. To clarify the matter, let's go through the choices one by one:
- Brass is an alloy made up of copper and zinc, which is considered a homogeneous mixture, also known as a solution in the broader sense.
- Air is a mixture of gases, primarily nitrogen, oxygen, and small amounts of other gases, and is considered a homogeneous mixture or solution.
- Copper, being an element, is neither a compound nor a mixture. So, it is not a solution.
- Vodka is a mixture of water and ethanol and sometimes other components; thus, it's a homogeneous mixture or solution.
Hence, copper is the correct answer, as it does not classify as a solution.