Which of the following devices operates at the network layer of the OSI model?

Multiple devices work at different layers of the OSI model. Each has its own function and a specific niche that cannot be taken up by the other device. For instance, the options A and b are needs as data link layer devices. They are AP and switch and serve to connect the device rather than perform the networking function.

On the other hand, the hub is required as a physical layer device that provides the physical means of connection. It is the router that performs the function of the network layer device in order to ensure optimum functioning of the OSI model.