The overall set in Malacca straight is to the NW, but from May to September there is a tendency for SE sets to prevail in some N and central parts.In this sentence,“set”refers to（）.

单项选择题（）indicates the weight of the vessel and is,therefore,according to a well known principle of physics,equal to the weight of the water it displaces.

A.Gross tonnage
B.Net tonnage
C.Displacement tonnage
D.Deadweight tonnage

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.

A.exhibited
B.established
C.constructed
D.built

单项选择题Integrated Bridge and Navigation Systems(IBS INS) provide excellent performance and reliable navigation under all conditions by（）.

A.integrating well-proven, harmonizing equipment
B.integrating all equipment in the bridge
C.an intelligent platform with ECDIS and Radar
D.the control center based on ECDIS

单项选择题The lowest point between two waves is called（）.

A.though
B.tough
C.through
D.trough