（）is the maximum speed of your ship?

单项选择题The fog is too thick. Don’t（）the radar.

A.switch on
B.switch off
C.close
D.open

单项选择题（）time will the pilot be available?

A.what
B.When
C.At what
D.At when

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（）.

A.in chief engineer's room
B.in chief officer's room
C.on the bridge
D.on deck

单项选择题All entries in Logbook,（）made, must not be erased.

A.once
B.whether
C.previous
D.just