Which of the following has been designated for "On-scene" communications in GMDSS?

Correct Answer: Option D — Ch-16 on VHF radiotelephone and 2174.5 kHz using MF SITOR.

IMO GMDSS regulations designate specific frequencies for on-scene communications to ensure coordination between distressed vessels and rescuers. VHF Channel 16 is the primary voice frequency, while 2174.5 kHz is the designated frequency for Narrow Band Direct Printing (NBDP) on-scene distress traffic.