Which of the following is a function of a router?

The function of a router primarily revolves around its ability to route data packets between different networks. This is fundamental to networking, as routers connect multiple networks and determine the best path for data transmission from the source to the destination. By analyzing network traffic, routers decide how to forward packets, which may involve using routing tables and algorithms to find the optimal routes.

A router operates at the network layer of the OSI model, where it adds and interprets information within the packet headers that dictate routing decisions. This capability is essential for inter-network communication, allowing disparate networks to communicate effectively.

While other devices and protocols handle functions such as data transmission at the physical layer, managing MAC addresses (which are primarily concerned with the data link layer), and performing error checking at the application layer (where session and presentation layers operate), these tasks are not the core functions of a router. A router's essential role is to facilitate connectivity and packet forwarding between different networks, making option C the correct choice.