单项选择题

In case a ship is in emergency or distress in any of 4 areas, it is required to use the continuous（）alert.

A.MF/HF
B.SART
C.EPIRB
D.any of A, B, C

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单项选择题

A.only automatically
B.only manually
C.both automatically and manually
D.only by remote control

单项选择题

A.be damaged
B.work normally regardless of harmful conditions
C.not wok though it is not in a bad condition

单项选择题

A.COSPAS-SARSAT
B.SATELLITE
C.terrestrial radio
D.INMARSAT