Concept:The idiom "sell someone a pup" means to cheat a customer by selling something defective or worthless.Explanation:The phrase describes dishonest dealing, not helpful service.Option A correctly captures the idea of tricking buyers into accepting faulty goods.Options B, C, and D refer to selecting well, overcharging, or exchanging items, none of which match the idiom.Answer:A. trick customers into buying faulty goods