Final answer:
Instant messaging operates as a decentralized network, where each user's device acts as a peer, facilitating direct communication without a central server.
Step-by-step explanation:
Instant messaging, where everyone can send and receive messages to one another, is an example of a Decentralized network (D). In a peer-to-peer network, each workstation (peer) can act as both a server and a client, with each being autonomous and facilitating the sharing of information in a distributed manner. Instant messaging platforms typically function in this decentralized way, allowing users to communicate directly with one another without necessitating a centralized server.