A.it necessary
B.it is necessary
C.it necessary to
D.necessary
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A.depend on
B.depending on
C.dependent on
D.depended on
A.exchange
B.to exchange
C.exchanging
D.exchanged
A.adherence to
B.adoption to
C.relaying on
D.usage of
A.keep silence
B.forbid transmission
C.change information
D.impose
A.taken
B.take
C.took
D.taked
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（）will form the basis for distress alerting and safety calling.
The quality of EGC messages is（）affected by the position of the ship, the time of reception and climatic conditions.
（）by an ice-breaker, it is important to maintain a continuous listening watch on the appropriate VHF channel and to maintain a proper look-out for sound and visual signals.
The advantage of geostationary satellites is（）.
By using（）system a ship can send a distress message and know with certainty it will be received.
Ship-to-ship distress alerting should be conducted by（）.
What following is not among the function of SOLAS ships?（）
Before GMDSS, if the radio officer on board is serious ill,（）.
SafetyNet is an international service for the broadcast and automatic reception of MSI by means of direct-printing through（）system.
Stations in the United States of America are grouped by states arranged in the alphabetical order of their（）.