Dacron sails，when not in use，may be damaged if（）.

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

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

A.vertical air movements
B.heavy rainstorms
C.horizontal air movements
D.any movement of moist air