Which of these hydrocarbons is a member of the benzene family?

• A. Ethyne.
• B. Toluene.
• C. Propane.
• D. Methane.

Answer: (B)

Understanding what defines the benzene family means looking for an aromatic six-membered ring with delocalized pi electrons. Toluene has a benzene ring with a single methyl group attached, so it stays within that aromatic family. The other options do not contain a benzene ring: ethyne is a linear molecule with a triple bond (not aromatic), while propane and methane are saturated alkanes with no rings or pi systems. Therefore, toluene is the member of the benzene family.