单项选择题
The luminous range of a light takes into account the（）.
A.glare from background lighting B.existing visibility conditions C.elevation of the light D.observer's height of eye
单项选择题 Restricted areas at locks and dams are indicated by（）.
单项选择题 Preferred channel buoys indicate the preferred channel to transit by（）.
单项选择题 Lighted white and orange buoys must show which color light?（）
