单项选择题
From your position you observe a rotating white and green light to the north. This light is most likely（）.
A.at an airport B.on a naval mine-countermeasures vessel C.Block Island North Light D.on a vessel engaged in public safety activity
单项选择题 From which type of cloud can a tornado or waterspout develop?（）
单项选择题 Freeboard is measured from the upper edge of the（）.
单项选择题 Frapping lines（）.
