Which of the following best describes a fatty acid that has no double bonds?

A fatty acid that has no double bonds is classified as a saturated fatty acid. This type of fatty acid is fully saturated with hydrogen atoms, meaning that every carbon atom in the chain is bonded to the maximum number of hydrogen atoms possible. This structure allows saturated fatty acids to pack closely together, resulting in a typically solid state at room temperature, which is characteristic of many animal fats.

In contrast, the other types of fatty acids mentioned involve double bonds. Unsaturated fatty acids, for instance, contain one or more double bonds, leading to kinks in their structure that prevent tight packing and therefore often results in a liquid state at room temperature. Polyunsaturated fatty acids are a subtype of unsaturated fatty acids with multiple double bonds. Trans fatty acids are typically unsaturated fats that have been altered through hydrogenation, which can create trans isomers but still contain double bonds.

Thus, the defining characteristic of saturated fatty acids—having no double bonds—makes this classification the correct answer.