单项选择题
A SEA ROOM TO BE KEPT FOR SAFETY AROUND A VESSEL，ROCK，PLATFORM，ETC.，OR THE PLACE ASSIGNED TO A VESSEL WHEN ANCHORED OR LYING ALONGSIDE A PIER，ETC means（）.
A.Port B.Commercial area C.Berth D.Roadstead
单项选择题 A flashing red light displayed at a single lock means that the lock（）.
单项选择题 A flashing green light displayed at a single lock means that the lock is（）.
单项选择题 You are on an ice-reinforced vessel about to enter packice. You should（）.
