单项选择题
A line of position formed by sighting two charted objects in line is called a(n)（）.
A.relative bearing B.range line C.track line D.estimated position
单项选择题 A lighthouse can be identified by its（）.
单项选择题 A lighted preferred-channel buoy may show a（）.
单项选择题 A light that has a light period shorter than its dark period is described as（）.
