单项选择题
A.white light whose characteristic is Morse (A) B.group-occulting white light C.composite group-flashing (2 + 1) white light D.composite group-flashing (2 + 1) red or green light
A preferred-channel buoy may be（）.A.letteredB.spherical...
单项选择题A preferred-channel buoy may be（）.
A.lettered B.spherical C.showing a white light D.All of the above
A plane that cuts the Earth’s surface at any angle and ...
单项选择题A plane that cuts the Earth’s surface at any angle and passes through the center will always form（）.
A.the equator B.a great circle C.a small circle D.a meridian
A plane that cuts the Earth’s surface and passes throug...
单项选择题A plane that cuts the Earth’s surface and passes through the poles will always form（）.
A.the equator B.a loxodromic curve C.a small circle D.a meridian
