单项选择题
When a buoy marks a channel bifurcation，the preferred channel is NOT indicated by（）.
A.the shape of an unlighted buoy B.the light color of a lighted buoy C.the color of the topmost band D.whether the number is odd or even
单项选择题 What is the major advantage of high altitude observations?（）
单项选择题 What is the light characteristic of a lighted，preferred-channel buoy? （）
单项选择题 What indicates a dual purpose buoy? （）
