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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The frequency（）the safety message will be transmitted shall be included in DSC safety call.
Every lifeboat which is fitted with a fixed two-way（）radiotelephone apparatus with an antenna which is separately mounted shall be provided with arrangements for sitting and securing the antenna effectively in its operating position.
In case a ship is in emergency or distress in any of 4 areas, it is required to use the continuous（）alert.
Distress traffic is the communication（）between the station in distress and the ships, aircraft, coast radio stations, coast earth stations and rescue centers participating in the rescue work.
SafetyNet is an international service for the broadcast and automatic reception of MSI by means of direct-printing through（）system.
For COSPAS-SARSAT system,（）usually transmit initial COSPAS-SARSAT alert.
SOLAS ships shall be equipped with（）.
The quality of EGC messages is（）affected by the position of the ship, the time of reception and climatic conditions.
If the beacon is mounted at a wrong place, it may（）by sea water, chemicals, exhaust and vibrations.
The priority of EGC messages is classified by（）.