单项选择题
The Consol navigation system，used in Russian and Northern European waters，can be used（）.
A.for precise navigation in coastal waters B.by measuring the phase difference of the dots and dashes C.as an aid to ocean navigation D.if the vessel is fitted with a special Consol receiver
单项选择题 The Class A EPIRB transmits a signal（）.
单项选择题 Survival craft EPIRBs (Class S) are（）.
单项选择题 Proper GMDSS watchkeeping includes（）.
