Which term refers to a back-up power source for Distress and Safety communications?

The correct term that refers to a back-up power source for Distress and Safety communications is "Reserve Source of Energy." This designation emphasizes the importance of having a reliable energy supply that can be activated in emergencies to support critical communication systems. In the context of safety and distress communications, maintaining functionality even when primary power sources fail is essential.

While "Emergency Diesel Generator" and "Emergency Back-up Generator" could refer to specific types of back-up power systems, they do not convey the broader concept of a reserve power source that might include various types of energy generation. "Reserve Source of Diesel Power," similarly, is too specific and does not encompass the variety of options that could be utilized for such emergencies, which might include battery systems, solar power, or other alternative energy sources that can also serve as a backup.

Therefore, "Reserve Source of Energy" is the most comprehensive and correct choice, reflecting the need for a versatile and reliable power supply in emergency scenarios.