Answer: (A) Knowledge
Explanation:
The knowledge gap is one of the hypothesis that basically explain about the knowledge that are distributed in the form of social system.
In the society the different people have their different opinions due to the different mindset, insufficient knowledge and also the difference in their age group also which leads to knowledge gap in the society.
According to the given question, the David is suffering from the knowledge gap as due to the lack of service and the spacial orders the customer are showing much interest in the bookstore.
Therefore, Option (A) is correct answer.