Final answer:
The correct answer is (a) functional obsolescence, which describes the decline in property utility and value due to outdated or impractical design that does not align with current demands.
Step-by-step explanation:
A property with an inefficient floor plan would suffer from functional obsolescence. This term refers to the loss in the utility and value of a property due to an outdated design that does not meet the current market expectations for functionality. Such obsolescence might occur because of poor design choices, such as awkward living spaces or an impractical layout that cannot be easily rectified without significant cost or reconstruction. In this context, functional obsolescence affects the desirability and therefore the economic value of the property.