Which system allows simultaneous two-way communication?

• A. Half-Duplex
• B. Simplex
• C. Full-Duplex
• D. SNR

Answer: (C)

The idea being tested is how a link supports two-way communication. When both ends can talk and listen at the same time, the system is operating in full-duplex mode. This is the mode that enables simultaneous two-way transmission and reception, like a normal telephone call where you can speak and hear at the same moment.

Simplex is one-way only, such as a broadcast channel where data travels in a single direction. Half-duplex allows two-way communication but not at the same time—you must take turns transmitting and receiving. SNR (signal-to-noise ratio) is about the quality of the signal relative to background noise, not about the direction or simultaneity of communication.

So, full-duplex is the best answer because it specifically describes concurrent two-way communication.