单项选择题
A.check the liferaft's way B.keep the liferaft end on to the sea C.reduce the possibility of capsizing or broaching D.right the raft if it inflates inverted
The reference datum used in determining the heights of ...
单项选择题The reference datum used in determining the heights of land features on most charts is（）.
A.mean sea level B.mean high water C.mean low water D.half-tide level
The purpose of the “set” hand on an aneroid barometer i...
单项选择题The purpose of the “set” hand on an aneroid barometer is to（）.
A.adjust the barometer B.indicate any change in the reading of the barometer C.provide a correction for height above sea level D.provide a correction for temperature changes
The error in the measurement of the altitude of a celes...
单项选择题The error in the measurement of the altitude of a celestial body，caused by refraction，increases as the（）.
A.horizontal parallax decreases B.observer's height above sea level increases C.humidity of the atmosphere decreases D.altitude of the body decreases
