What group of letters is transmitted over RATT three times in urgency signals?

The correct answer is "Safety" because this term is specifically used in maritime and aviation communications to indicate that a situation requires immediate attention regarding safety. In RATT (Radio Teletype), urgency communications follow established standards to convey critical messages effectively.

The repetition of the term "Safety" three times serves to emphasize the seriousness of the information being transmitted, ensuring that recipients understand that the message pertains to a safety concern. This practice helps to grab the attention of those monitoring the communication, stressing the importance of the message and prompting an appropriate response.

Other terms, while they may hold significance in different contexts, do not have the same urgency or standardization associated with safety communications in RATT, which is why they do not fit in this context.