单项选择题
The mariner must be the final judge of the reliance he can place on the information given in the Admiralty charts and other publications,since they（）.
A.may always be complete and up-to-date B.may not always be complete and up-to-date C.may sometimes be complete and up-to-date D.may not sometimes be complete and up-to-date
单项选择题 A light is（）from Changshanzui,the SE extremity of the island.
单项选择题 Integrated Bridge and Navigation Systems(IBS/INS) provide excellent performance and reliable navigation under all conditions by（）.
单项选择题 The lowest point between two waves is called（）.
