When requesting a direct TELEX connection to a vessel's Inmarsat-B terminal, (i.e. making a SITOR call to an Inmarsat-B unit) the GMDSS operator must:

Correct Answer: Option B — DIRTLX, 0, Ocean Area Code, TELEX number, +.

Direct-dialing an Inmarsat-B terminal via a coast station requires the DIRTLX command followed by the access code '0', the ocean region code, and the terminal's TELEX number. This specific format allows the coast station's automated controller to route the call through the satellite network to the vessel.