单项选择题
In navigation the abbreviation “DF” refers to（）.
A.Deep Flood B.Direction Finder C.Double Freeboard D.Dangerous Fertilizer
单项选择题 There are many navigational aids（）.
单项选择题 All entries in Logbook,（）made, must not be erased.
单项选择题 The pilot said he（）our vessel directly to berth.
