单项选择题
With the help of modern technology, ships are able to receive automated broadcast of safety messages（）.
A.by day or at night
B.almost round the clock
C.somewhat and sometime
D.from sunrise and sunset
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相关考题
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单项选择题
A radio determination system based on the comparison of reference signals with radio signals reflected,or retransmitted from the position to be determined,is（）.
A.DF
B.Radar System
C.DSC System
D.COSPAS-SARSAT -
单项选择题
What information will a distress alert contain?（）
A.nature of distress
B.type of assistance required
C.course and speed and time at which the information was recorded
D.A, B, C are all right -
单项选择题
The ARQ mode should be applied（）.
A.when two stations communicate with each other
B.in any radio system and at any time
C.when one ship sends a message to another station
D.for communication among some stations
