Which of the following is an example of functional obsolescence?

Functional obsolescence refers to a decline in the desirability or utility of a property due to design features or inadequacies that are no longer considered modern or desirable in the current market. The option that indicates a lack of air conditioning in a home exemplifies this concept because, in many regions, particularly warmer climates, air conditioning is considered a standard amenity. The absence of this feature can make the home less appealing to buyers, thus diminishing its value compared to other homes that have modern conveniences, making it a clear case of functional obsolescence.

In contrast, deferred maintenance refers to issues related to the physical state of a property, such as not keeping up with necessary repairs, which does not directly involve the outdated features of a property's design or utility. A building located in a vibrant area typically does not relate to functional obsolescence, as location is largely beneficial. Lastly, modern architectural styles are typically seen as desirable and likely add to a property's value, rather than detract from it.