（）reters to be amount of water vapour in the air.

单项选择题（）is used for receiving maritime safety information which is automatically printed by the receiver.

A.NAVETEX receiver
B.Search and Rescue Transponder
C.Emergency Position Indicating Radio Beacon
D.Digital selective calling

单项选择题（）is used for providing homing signals from survival craft for detection by 9Ghzradar.

A.NAVETEX receiver
B.Search and Rescue Transponder
C.Emergency Position Indicating Radio Beacon
D.Digital selective calling

单项选择题（）is used for calling and replying,and for transmitting acknowleding and relaying distress alerts.

A.NAVETEX receiver
B.Search and Rescue Transponder
C.Emergency Position Indicating Radio Beacom
D.Digital selective calling

单项选择题（）provides a paper trace of course steered by the vessel against time.

A.The echo sounder
B.The radar
C.The course recorder
D.The direction finder

单项选择题（）is a radio receiver with ablity to sense direction of the incoming radio waves.

A.The echo sounder
B.The radar
C.The course recorder
D.The direction finder