What action should you take after sending a false Distress alert on 8 MHz?

Correct Answer: Option B — Make an "ALL SHIPS" call on 8291.0 kHz canceling the alert.

IMO GMDSS procedures mandate that false alerts must be canceled immediately. For HF DSC, the operator must broadcast an 'ALL SHIPS' voice announcement on the associated radiotelephone frequency (8291.0 kHz for 8 MHz) to notify stations that the previous digital alert was erroneous and should be disregarded.