Which of the following is not a device used in data communication? A. modem B. multiplexer C. statistical multiplexer D. front-end processor E. All of the above

The correct answer is E. All of the above.

A modem is a device that modulates and demodulates signals, allowing computers to communicate over telephone lines. A multiplexer is a device that combines multiple signals

into a single signal, allowing multiple devices to share a single communication channel. A statistical multiplexer is a type of multiplexer that uses statistical techniques to share a communication channel more efficiently. A front-end processor is a computer that is used to offload tasks from a main computer, such as handling input and output.

While all of these devices are used in data communication, a front-end processor is not a device that is used to transmit or receive data. It is a device that is used to offload tasks from a main computer, such as handling input and output.