Cholesterol contains four fused hydrocarbon rings.

• A. Three fused rings
• B. Five fused rings
• C. Four fused rings
• D. Six fused rings

Answer: (C)

Steroids are defined by a four-ring hydrocarbon skeleton. This nucleus is three six-membered rings fused to one five-membered ring, forming the cyclopentanoperhydrophenanthrene structure. In cholesterol, this four-ring system serves as the rigid core that defines the molecule’s shape; the rings share carbon atoms and bonds, not just sit side by side, which locks parts of the molecule into fixed orientations. While cholesterol also has a hydroxyl group and a hydrocarbon side chain, the essential framework—the four fused rings—remains the defining feature.