单项选择题
A.litmus paper B.combustible gas indicator C.oxygen breathing apparatus D.oxygen indicator
Deck beams on a ship are generally spaced at equal inte...
单项选择题Deck beams on a ship are generally spaced at equal intervals and run（）.
A.longitudinally B.vertically C.transversely D.intermittently
Day-shapes must be displayed（）.A.between sunset and sun...
单项选择题Day-shapes must be displayed（）.
A.between sunset and sunrise B.only between 8 AM and 4 PM C.during daylight hours in any visibility D.during daylight hours in unrestricted visibility only
Daylight savings time is a form of zone time that adopt...
单项选择题Daylight savings time is a form of zone time that adopts the time（）.
A.one zone to the east B.one zone to the west C.two zones to the east D.two zones to the west
