Fatty acids may be saturated or unsaturated.

• A. Only saturated can be fatty acids
• B. Only unsaturated can be fatty acids
• C. Fatty acids may be saturated or unsaturated
• D. They are always polyunsaturated

Answer: (C)

Saturation describes how many carbon–carbon double bonds are in the fatty acid chain. A fatty acid with no double bonds is saturated; the chain is straight and can pack tightly, often making it solid at room temperature. An unsaturated fatty acid has one or more double bonds; most natural ones are cis, which introduces kinks in the chain, preventing tight packing and generally lowering the melting point so they’re liquid at room temperature. They can be monounsaturated (one double bond) or polyunsaturated (two or more). So, fatty acids may be saturated or unsaturated, which is why this statement is correct. The other options misstate the reality by claiming exclusivity or that all fatty acids are polyunsaturated.