单项选择题
A mid-channel buoy，if lighted，will show a（）.
A.fixed red light B.Morse (A) white light C.green light D.flashing red light
单项选择题 A line on the Earth parallel to the equator is a（）.
单项选择题 A line of position formed by sighting two charted objects in line is called a(n)（）.
单项选择题 A lighthouse can be identified by its（）.
