Explanation: H3E (single-sideband full carrier) is the preferred mode for 2182 kHz because it is more spectrally efficient and uses less power than A3E (double-sideband full carrier) for the same effective communication range. However, A3E was the established mode for maritime radiotelephone distress before the widespread adoption of SSB. To ensure older vessels equipped with vital, dedicated A3E emergency equipment could still transmit distress calls during the transition to GMDSS (Global Maritime Distress and Safety System) and beyond, its use was permitted *only* for equipment **solely intended for distress and safety communications**. This provision allowed older, critical safety gear to remain operational without requiring immediate and costly upgrades. Options B and C are incorrect because GMDSS implementation generally mandated more efficient modes, not less efficient ones, for new equipment. Option D is incorrect as public correspondence would typically utilize the most efficient and modern modes available, not older A3E.