单项选择题
A.transmit distress signal
B.send response signal
C.transmit the signal of ship‟s position
D.be start by X-band radar
单项选择题 Distress traffic（）all messages relating to the immediate assistance required by the ship in distress, including search and rescue communications and signals for locating.
单项选择题 The transmission of a（）indicates that a ship is in distress and requires immediate assistance.
单项选择题 The GMDSS is composed of（）.