Concept:Self-service is a retail trend where customers freely access and select products themselves.Explanation:In self-service shops or stores, customers move freely among displayed products.They pick the items they want without the help of a sales attendant.After selecting, they pay at a central checkout point.This method gives consumers direct access to a wide variety of products.Branding, after-sales services, and vending machines do not primarily provide free access to different products in this open-retail sense.Answer:C. self-services