单项选择题 If you saw flames aboard a vessel but could see the vessel was not on fire，you would know that the（）.

单项选择题 If there are a number of survivors in the water after abandoning ship，they should（）.

单项选择题 If the named port is one at which no tugs are ever obtainable，and the chartered vessel can not，by reason of her size，reach that port without the assistance of tugs，the port is（）.