Which ARQ code sequence is used for sending synoptic weather, switching control from one station to another, and terminating phasing with a coast station?

The correct answer is based on the specific code sequence used in GMDSS (Global Maritime Distress and Safety System) communication for various operational messages. The ARQ (Automatic Repeat reQuest) code sequence serves distinct functions in maritime communication.

The chosen code sequence is designed to perform multiple crucial tasks: sending synoptic weather information, initiating control switches between stations, and managing the termination of phasing with a coast station. Each part of the sequence has a defined purpose, and OBS+ signifies an observation report. This is pertinent for transmitting weather information. The subsequent symbols, like +? and BRK+, specify the kind of interactions required for control and sequencing in the communication process.

In contrast, the other options contain sequences that do not accurately encapsulate the functions necessary for the tasks mentioned. For instance, other sequences may involve different operational commands or combinations that are not intended for the same types of messages. Thus, the correct sequence’s structure allows for clear communication of synoptic weather, effective switching control, and proper termination of station phasing.