Coast Pilots and navigational charts are kept corrected and up-to-date by using the（）.

A.are sheet or layer clouds
B.have undergone great vertical development
C.are middle or high altitude clouds
D.are rain clouds

A.as a mass of warm，humid air rises into the atmosphere and cools，condensing moisture into small droplets
B.as winds blow across bodies of water，the sun causes the moisture to be absorbed and move upward forming clouds
C.dry air compresses moisture from the atmosphere into clouds
D.when the relative humidity of the atmosphere is low

A.high pressure fluid accumulators
B.driving air-powered plunger pumps
C.filling open-circuit breathing systems
D.bladder-type accumulators