单项选择题
A.what B.When C.At what D.At when
In navigation the abbreviation “DF” refers to（）.A.Deep ...
单项选择题In navigation the abbreviation “DF” refers to（）.
A.Deep Flood B.Direction Finder C.Double Freeboard D.Dangerous Fertilizer
There are many navigational aids（）.A.in chief engineers...
单项选择题There are many navigational aids（）.
A.in chief engineer's room B.in chief officer's room C.on the bridge D.on deck
All entries in Logbook,（）made, must not be erased.A.onc...
单项选择题All entries in Logbook,（）made, must not be erased.
A.once B.whether C.previous D.just
