What are the mandatory DSC watchkeeping bands/channels?

Correct Answer: Option C — 8 MHz HF DSC, 1 other HF DSC, 2 MHz MF DSC and VHF Ch-70.

Mandatory GMDSS DSC continuous watchkeeping frequencies include VHF Channel 70, MF 2 MHz (2187.5 kHz), the 8 MHz HF band (8414.5 kHz), and one additional HF DSC frequency based on propagation.