单项选择题
A.receiving messages/one station
B.transmission/ one coast station or ship
C.communicating /one ship
D.contacting/other
单项选择题 The SART should have sufficient battery capacity to operate in the stand-by condition for（）hours and should continuously work for（）hours.
单项选择题 It is required that ships proceeding at sea should keep continuous watch on（）.
单项选择题 The transmission of a（）indicates that a ship is in distress and requires immediate assistance.