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
单项选择题 Radio beacon can be activated（）in case of distress.
单项选择题 If the beacon is mounted at a wrong place, it may（）by sea water, chemicals, exhaust and vibrations.
单项选择题 By using（）system a ship can send a distress message and know with certainty it will be received.
