In the context of computer networks, which of the following is a data…

Concept: In a communication channel, the data-transmission (or communication) mode describes the direction in which data can flow between two devices. There are exactly three standard modes — simplex (one direction only), half-duplex (both directions, but only one at a time), and full-duplex (both directions simultaneously).

Applying it to the listed items:

• Simplex — a recognised mode: data travels in a single, fixed direction (e.g. keyboard to computer, a TV broadcast).

• Half Simplex — not a defined term in networking. The genuine mode with a 'half' qualifier is half-duplex; 'half simplex' is a made-up combination and is not a transmission mode.

• Full Duplex — a recognised mode: data travels in both directions at the same time (e.g. a telephone call).

Result: Of the three listed items, the valid transmission modes are Simplex (I) and Full Duplex (III). Item II is the trap, because 'half simplex' is easily confused with the real mode half-duplex.

Cross-check: Counting the standard modes gives three — simplex, half-duplex, full-duplex. Neither half-duplex nor 'half simplex' appears in the list as a separate correct item, so any choice that includes item II is wrong.