Step 1: Approach
Match the position of the OH group with the name of each class.
Step 2: Classes
- Aliphatic: OH on an open-chain saturated carbon.
- Allylic: OH on the carbon next to a $\text{C=C}$.
- Vinylic: OH on a $\text{C=C}$ carbon itself.
- Aromatic: OH on a carbon in the side chain of a benzene ring, such as $\text{C}_6\text{H}_5\text{CH}_2\text{OH}$.
Step 3: Conclusion
The question asks for OH on the side chain of the aromatic ring, which defines aromatic alcohols, option (C).
Final Answer:
An OH on the side chain of an aromatic ring defines an aromatic alcohol, option (C).
\[ \boxed{\text{Aromatic alcohols}} \]