单项选择题
A.painted color B.light color and phase characteristic C.type of structure D.All of the above
A lighted preferred-channel buoy may show a（）.A.fixed r...
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
A light that has a light period shorter than its dark p...
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
A light having characteristics which include color vari...
单项选择题A light having characteristics which include color variations is defined as（）.
A.switching B.alternating C.oscillating D.fluctuating
