All country codes which are transmitted by MF/HF SITOR are preceded by which character(s)?

Correct Answer: Option A — 0

In SITOR (Simplex Telex Over Radio) operations, the digit '0' is the standard prefix for country codes when dialing international telex numbers. This follows the CCITT (now ITU-T) Recommendation F.69, which governs the international telex service numbering plan for automated routing through coast stations.