Final answer:
The parties that can serve as the principal in a transaction are the seller, buyer, and landlord, as they have the authority and responsibility over the respective transactions.
Step-by-step explanation:
The parties that may serve as the principal in a transaction include the seller, buyer, and landlord. A principal in a transaction is a person or entity that has the primary responsibility and authority to engage in a transaction. For instance, the seller is the principal when they own the goods or property being sold and have the authority to transfer ownership to the buyer. The buyer becomes the principal when they initiate the purchase and have the authority to negotiate and accept terms. Finally, the landlord serves as the principal in a rental transaction, as they own the property and have the right to lease it to tenants.