单项选择题

All coast radio stations（）DSC installed for VHF and HF.

A.have
B.had
C.are having
D.have had

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单项选择题

The vessel has stayed in port for seven days because she needs（）.

A.repairs
B.repairing
C.repaired
D.being repaired

单项选择题

（）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.

A.which is assisted
B.that assist you
C.when you assisted
D.when being assisting

单项选择题

The advantage of geostationary satellites is（）.

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