Which of the following is a key feature of a modem?

• A. Allows wireless access to the internet
• B. Manages local area networks
• C. Modulates and demodulates signals for data transmission
• D. Controls firewall settings

Answer: (C)

A modem's primary function is to modulate and demodulate signals, which is essential for enabling data transmission over various types of communication channels. Modulation refers to the process of converting digital data from a computer into an analog signal that can be transmitted over phone lines or other media, while demodulation is the reverse process, converting incoming analog signals back into digital data for the computer to interpret. This capability is crucial for internet connectivity, allowing computers to send and receive data over telephone lines, cable systems, or other infrastructures.

In contrast, other choices include functions that are not related to what a modem does. For instance, enabling wireless internet access is a feature of wireless routers rather than modems. Managing a local area network is primarily the role of networking equipment such as switches and routers. Additionally, controlling firewall settings involves security devices or software that monitor and control incoming and outgoing network traffic, which is separate from the modulation and demodulation tasks performed by a modem. Thus, the correct answer reflects the fundamental role of a modem in facilitating internet communication through its ability to convert signals between digital and analog formats.