Explanation: SITOR-ARQ (Simplex Teletype Over Radio - Automatic Repeat reQuest) is a robust data mode designed for reliable communication over challenging HF channels, particularly in maritime operations. Its ARQ mechanism ensures data integrity through error detection and retransmission. The system operates using a precise timing scheme. The standard signaling rate for SITOR-ARQ is **100 baud**. The critical element for its ARQ functionality is the timed interval between transmission bursts. The system allows for a **240 ms interval** between a master station's transmission and a slave station's acknowledgement or vice versa. This specific interval accounts for propagation delay over long distances and the necessary turnaround time for radio equipment switching between transmit and receive. Options B and C present incorrect baud rates or physically impossible/impractical intervals for an ARQ system operating on HF, making A the only correct choice reflecting the established technical specifications for SITOR-ARQ.