Which of the following types of transactions is least likely to use a person-to-person (P2P) payment system?

The least likely transaction to utilize a person-to-person (P2P) payment system is when a person is buying groceries at a supermarket. P2P payment systems are typically designed for direct transfers between individuals rather than for commercial transactions involving established businesses.

In a grocery store setting, purchases are usually made through traditional payment methods such as debit or credit cards, cash, or mobile payment systems integrated directly with the merchant, as these provide greater convenience and efficiency for transactions involving point-of-sale terminals. The supermarket acts as a retailer, and the transaction is a commercial exchange rather than a peer-to-peer interaction, making it less suitable for P2P payment platforms that are primarily aimed at facilitating transactions between individuals.

In contrast, the other options all involve direct transfers between individuals or interactions that are better served by P2P systems. Online donations, transferring money to a friend, and payment for items on an auction site all reflect scenarios where individuals engage in financial exchanges that are characteristic of P2P payment systems.