A.are sheet or layer cloudsB.have undergone great verti……

单项选择题Clouds form（）.

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

单项选择题Clean air standards referred to as “Grade D” apply to compressed air for use in（）.

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

单项选择题Class I and II private aids to navigation in or along navigable waters of the United States are listed in the（）.

A.Sailing Directions
B.Light List
C.List of Private Aids
D.Aids to Navigation Manual

单项选择题Chronometer error may be found by（）.

A.radio time signal
B.comparison with a timepiece of known error
C.applying the prevailing chronometer rate to previous readings
D.All of the above

单项选择题Charts showing the coast of Mexico are produced by the United States（）.

A.National Geospatial-Intelligence Agency
B.Coast Guard
C.Naval Observatory
D.National Ocean Service