单项选择题
A.Humidity B.Temperature C.Precipitation D.Wind
（）reters to be amount of water vapour in the air.A.Humi...
单项选择题（）reters to be amount of water vapour in the air.
（）is used for receiving maritime safety information whi...
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
（）is used for providing homing signals from survival cr...
单项选择题（）is used for providing homing signals from survival craft for detection by 9Ghzradar.
