David's marketing research returned the finding that customers were staying away from his bookstore because of a lack of services like gift cards, return policies, and special orders. david was shocked. "nobody ever asks about that stuff! if it were that important, people would ask about it." david is likely suffering from

Knowledge gap.                        

Explanation:

Knowledge gap: The term knowledge gap is defined as a theory related to communication which is formerly concerned or focused about the unequal distribution of a piece of information related to society and can be accessed through knowledge being existed in the socioeconomic status.

The knowledge gap states that a person having a higher socioeconomic status gain information through mass media earlier as compared to a person of lower socioeconomic status and this results in creating a knowledge gap between these two segments of a particular society.

In the question above, David is likely suffering from a knowledge gap.