Concept:A retail business that uses catalogues and delivers goods by post is called a mail order firm.
Explanation:A mail order firm advertises its products through catalogues.
Customers choose items from the catalogue and place orders by post, phone, or online.
Goods are then delivered to customers through the post or other delivery services.
This matches the description in the question.
Chain stores, department stores, and shopping malls operate through physical outlets, not by post.
Answer:Mail order firm (Option C)