单项选择题
A vessel showing a green light over a white light in a vertical line above the level of the sidelights is（）.
A.engaged in underwater construction B.under sail and power C.a pilot vessel D.trawling
单项选择题 A vessel servicing a pipeline during the day shall display（）.
单项选择题 A vessel sailing shall keep out of the way of all of the following vessels except a vessel （）.
单项选择题 A vessel or object being towed astern shall display a(n)（）.
