单项选择题
A celestial body’s complete orbit around another body is（）.
A.a rotation B.a revolution C.space motion D.nutation
单项选择题 A celestial body will cross the prime vertical circle when the latitude is numerically（）.
单项选择题 A casualty report of an intentional grounding of a ship is required under what condition?（）
单项选择题 A buoy with a composite group-flashing light indicates a(n)（）.
