【单选题】18what 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 tothe NBDP follow-on communications frequency.
B.
The operator should immediately set continuous watch on the radiotelephone frequency that is associated with 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 Lhat is asso- ciated with frequency band onwhich the distress alert was received.