（）is a silvery cloud in the front of feathers or fibres seen high up against a blue sky.

A.Tides
B.Sea
C.Swell
D.Wind

A.Falling barometric pressure
B.Rising barometric pressure
C.The circulations of winds
D.The change of wind direction

A.The persence of cirrus clouds
B.The low-hanging stratus clouds
C.The altocumulus clouds
D.The massive cumulus clouds