Deck beams on a ship are generally spaced at equal intervals and run（）.

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

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

单项选择题Dacron sails，when not in use，may be damaged if（）.

A.left in the sunlight
B.stowed wet
C.washed with soap
D.folded frequently

单项选择题Cyclones that have warm sectors usually move（）.

A.westerly
B.parallel to the isobars in the warm sector
C.toward the nearest high pressure area
D.faster than the accompanying cold front

单项选择题Cumulus clouds that have undergone vertical development and have become cumulonimbus in form，indicate（）.

A.clearing weather
B.that a warm front has passed
C.probable thunderstorm activity
D.an approaching hurricane or typhoon