Concept:An agent acts on behalf of another person, known as the principal, to create legal contracts with third parties.
Explanation:The key role of an agent is to represent the principal and bring about contractual relationships with outsiders.
Agents have the authority to negotiate and enter into agreements on the principal's behalf.
A merchant simply buys and sells goods for profit, not necessarily as a representative.
A consignee receives goods for sale or custody, while a consignor sends goods to another party.
Only an agent performs the specific function of linking the principal to third parties through contracts.
Answer:D. an agent.