Which type of computer functions as a central repository, providing hardware, software, and other resources to multiple clients connected over a network?

Computers connected on a network often play different roles, and one common arrangement is for one machine to centrally hold resources that other machines can access.

A server is a computer specifically set up to store and manage resources, such as files, applications, databases, or printers, and to make those resources available to other computers, called clients, that connect to it over a network. This central role, providing hardware, software, or data resources to multiple connected clients, is exactly what defines a server in a network.

The other options describe computers with different roles. A workstation is a powerful computer used by an individual for demanding tasks such as graphic design or engineering work, not for centrally serving other machines. A mainframe is a very large, high-capacity computer used mainly by big organisations for bulk data processing, but its defining feature is raw processing capacity, not specifically serving client requests over a network. A supercomputer is built for extremely fast, large-scale scientific or numerical computation, again not for the client-server resource-sharing role described.

When a question describes a machine acting as a "central repository" that provides resources to "multiple clients" over a network, that specific client-server relationship identifies a server.