Concept:After-sales service is the support given to a customer after a product has been sold.Explanation:The retailer deals directly with final consumers.Thus, the retailer is usually responsible for after-sales services such as installation, handling complaints, exchanges, and repairs.Wholesalers and agents are mostly involved in bulk distribution and do not give direct after-sales service to final consumers.An entrepreneur organises the business but does not always render after-sales service directly.Answer:A. a retailer