單項選擇題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


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1.單項選擇題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

2.單項選擇題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

3.單項選擇題It is required that ships proceeding at sea should keep continuous watch on（）.

A.VHF channels 16 and 13
B.Appropriate DSC distress and safety frequencies
C.INMARSAT TDM message channel
D.VHF channel 70 and channel 8

4.單項選擇題General radio communications in the global system are those between（）concerning the management and operation of the ships and may have impact on their safety.

A.SAR party and the ship in distress
B.SAR authorities and the ship in distress and survival craft
C.A ship station and any coast station
D.Ship stations and shore-based communication network

5.單項選擇題why do some stations keep silence?（）

A.Because they are not engaged in the distress traffic
B.they will affect the transmission of the distress traffic
C.The powers of these stations are very weak
D.They are not in charge of search and rescue