Which of the following best defines a merchant?

The best definition of a merchant is a business that accepts payments via credit or debit cards. This definition encompasses the essential role of a merchant in the payment ecosystem, which is to facilitate transactions by allowing customers to use their credit or debit cards for purchases. Merchants engage in selling goods or services and provide a point of sale where customers can make payments electronically, which is a fundamental aspect of modern commerce.

While other definitions, such as those involving companies that issue cards, process payments, or provide banking services, touch on related components of the payment system, they do not capture the specific function of a merchant. In essence, the merchant is the entity where the transaction occurs and is directly involved in accepting payments from customers, making option B the most accurate.