A.has been used
B.have been used
C.has used
D.have used
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A.have
B.had
C.are having
D.have had
A.repairs
B.repairing
C.repaired
D.being repaired
A.which is assisted
B.that assist you
C.when you assisted
D.when being assisting
A.the range of antenna can cover everywhere in the world
B.we can know the ship’s exact position
C.that the distress alert can be located as soon as possible
D.antenna of permanent earth stations may be directed towards fixed points in the sky
A.which
B.on which
C.at which
D.in which
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（）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.
SOLAS ships shall be equipped with（）.
We consider（）send a helicopter with medical facilities to the distress area.
COSPAS-SARSAT is intended to be used for（）.
International Navtex service means the coordinated broadcast and automatic reception on（）khz of maritime safety information by narrow-band direct-printing telegraphy using English language.
All coast radio stations（）DSC installed for VHF and HF.
On-scene communications will normally take place between（）.
In case a ship is in emergency or distress in any of 4 areas, it is required to use the continuous（）alert.
Radio beacon can be activated（）in case of distress.
The rescue coordination center may（）on stations which interfere with traffic.