Which of the following watches must a compulsory vessel maintain when sailing in Sea Area A1?

Correct Answer: Option D — A continuous DSC watch on Ch-70.

IMO GMDSS regulations require vessels in Sea Area A1 to maintain a continuous watch on VHF DSC Channel 70. This frequency is dedicated to digital selective calling for distress, urgency, and safety alerts, ensuring immediate notification to shore-based authorities and nearby vessels within VHF range of coastal stations.