What is the action that a GMDSS Radio Operator should take when a DSC distress alert is received?

A
No action is necessary, as the DSC control unit will automatically switch to the NBDP follow-on communications frequency.
B
The operator should immediately set continuous watch on the radiotelephone frequency that is associated with the frequency band on which the distress alert was received.
C
The Operator should immediately set continuous watch on VHF channel 70.
D
The Operator should immediately set continuous watch on the NBDP frequency that is associated with the frequency band on which the distress alert was received.
E