The correct answer is A. Modulator Demodulator.
A modem is a device that converts digital signals to analog signals and vice versa. This is necessary for communication between computers and other devices over telephone lines, which are designed to carry analog signals.
The modem modulates the digital signal into an analog signal that can be transmitted over the telephone line. The receiving modem then demodulates the analog signal back into a digital signal that can be understood by the computer.
Modems are typically used to connect computers to the internet, but they can also be used to connect computers to other devices, such as fax machines and printers.
Option B is incorrect because it does not describe the function of a modem. A monetary devaluation exchange mechanism is a system that allows countries to exchange their currencies at a different rate than the official exchange rate.
Option C is incorrect because it does not describe the function of a modem. Memory demagnetization is the process of erasing data from a magnetic storage device, such as a hard drive or floppy disk.
Option D is incorrect because it does not describe the function of a modem. Monetary demarcation is the process of dividing a country’s currency into different denominations.