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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The frequency（）the safety message will be transmitted shall be included in DSC safety call.
The advantage of geostationary satellites is（）.
If the beacon is mounted at a wrong place, it may（）by sea water, chemicals, exhaust and vibrations.
COSPAS-SARSAT is intended to be used for（）.
As each MSI message will have a unique identity, the printing of messages already received correctly is（）.
We consider（）send a helicopter with medical facilities to the distress area.
Radiotelephony communication or radio telex communication or both will be carried out by terrestrial or satellite means,（）the equipment fitted on ship and the area in which the incident occurs.
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.
By using（）system a ship can send a distress message and know with certainty it will be received.
On-scene communications will normally take place between（）.