Which of the following is a type of transmission mode? I. Simplex mode II.…

Concept: Data communications defines exactly three transmission modes based on the direction and simultaneity of data flow between two devices — Simplex (data flows in one direction only), Half-duplex (data flows in both directions, but only one direction is active at a time), and Full-duplex (data flows in both directions simultaneously, often shortened to "Duplex"). No other named mode exists in this standard classification.

Application: Checking each Roman-numeral statement against this classification:

• I. Simplex mode — matches the standard one-direction-only mode.

• II. Half simplex mode — no such mode exists in the standard classification; the two-way, one-direction-at-a-time mode is named Half-duplex, not "Half simplex".

• III. Duplex mode — matches Full-duplex, the standard simultaneous two-way mode.

So only statements I and III name valid transmission modes.

Cross-check: Comparing against the offered combinations confirms this:

• "I and II" and "II and III" both include the non-existent term "Half simplex", so both are ruled out.

• "I, II and III" is ruled out for the same reason.

• "I and III" is the only combination containing solely the two genuinely valid mode names — Simplex and Duplex (Full-duplex).