Which of the following is a correctly formatted Inmarsat-C address book entry for sending TELEX communications to a vessel in the IOR?

Correct Answer: Option D — 583446976519

The 583 prefix is the designated identifier for the Indian Ocean Region (IOR) in Inmarsat-C TELEX addressing. The sequence 583446976519 correctly adheres to this format, allowing the GMDSS terminal to route the TELEX message through the appropriate IOR-based Land Earth Station to the recipient.