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)（）.

A.relative bearing
B.range line
C.track line
D.estimated position

单项选择题A lighthouse can be identified by its（）.

A.painted color
B.light color and phase characteristic
C.type of structure
D.All of the above

单项选择题A lighted preferred-channel buoy may show a（）.

A.fixed red light
B.Morse (A) white light
C.composite group-flashing light
D.yellow light

单项选择题A light that has a light period shorter than its dark period is described as（）.

A.flashing
B.pulsating
C.occulting
D.alternating

单项选择题A light having characteristics which include color variations is defined as（）.

A.switching
B.alternating
C.oscillating
D.fluctuating