单项选择题 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.

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（）.