A preferred-channel buoy may be（）.

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

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

单项选择题A plane perpendicular to the polar axis will never form what line on the Earth’s surface? （）

A.Great circle
B.Equator
C.Small circle
D.Meridian

单项选择题A parallel of latitude other than the equator is a（）.

A.great circle
B.loxodromic curve
C.small circle
D.gnomonic curve

单项选择题A nun buoy will（）.

A.be green in color
B.have an even number
C.be left to port when entering from seaward
D.be cylindrical in shape