Which statement describes monounsaturated fatty acids?

• A. They are liquids at room temperature, such as oleic acid in olive oil
• B. They have more than one double bond
• C. They are all essential fatty acids
• D. They are always solid at room temperature

Answer: (A)

Monounsaturated fatty acids have one double bond in their hydrocarbon chain, which introduces a small kink that prevents tight packing. This lowers the melting point, so these fats are typically liquids at room temperature. Oleic acid is a classic example and is the main fatty acid in olive oil, contributing to its liquid nature even though olive oil can solidify when very cold.

The other statements don’t fit because a second double bond would make a polyunsaturated fat, not monounsaturated; essential fatty acids are a specific subset of polyunsaturated fats that must be obtained from the diet, not all MUFAs; and fats with any unsaturation generally aren’t always solid at room temperature—saturated fats are the ones that are typically solid.