The correct answer is: C. Multiplexer
A multiplexer is a device that combines multiple signals into a single signal. This can be done in a number of ways, but the most common is to use time-division multiplexing (TDM). TDM divides the available bandwidth into time slots, and each signal is assigned a specific time slot. This allows multiple signals to be transmitted over a single channel without interfering with each other.
A modem is a device that converts digital signals into analog signals and vice versa. This is necessary for communication over telephone lines, which are designed to carry analog signals. Modems are typically used to connect computers to the internet, but they can also be used to connect other devices, such as fax machines and printers.
A network is a group of computers that are connected together so that they can share information and resources. Networks can be local area networks (LANs), which are typically confined to a single building or office, or wide area networks (WANs), which can cover large geographical areas.
The answer is C. Multiplexer because it is the only option that describes a device that combines multiple signals into a single signal. The other options describe devices that do not perform this function.