单项选择题
The shortest distance between any two points on earth defines a（）.
A.small circle B.great circle C.rhumb line D.hyperbola
单项选择题 The positions and characteristics of lights and buoys shown within the port area are（）.
单项选择题 The period of a lighted aid to navigation refers to the（）.
单项选择题 The nominal range of a light may be accurately defined as the maximum distance at which a light may be seen（）.
