Which scenario is least likely to cause a coast station to break the phased radio connection during ARQ communications?

The choice of entering "NNNN" at the end of the message is least likely to cause a coast station to break the phased radio connection during ARQ (Automatic Repeat reQuest) communications because "NNNN" serves a specific purpose in the context of GMDSS operations. It is used as a signal to indicate the end of a message, which helps the receiving station conclude the transmission and process the received data appropriately without misunderstanding or ambiguity.

In contrast, scenarios like a high error percentage in repeat requests could lead to frustrations with data integrity, prompting the system to terminate or break the connection while other scenarios, such as manual interruptions or operator commands, could actively cause a disconnection if they interfere with ongoing transmissions. Ultimately, entering "NNNN" is a procedural step that an operator would take as part of normal communication, ensuring the message is clearly ended rather than causing disruption.