单项选择题
（）is a high layer of cloud in the front of small flakes or cauhflower,white in colour with no dark shadows in between.
A.Cirrostratus B.Cirrus C.Cirrocumulus D.Altostratus
单项选择题 （）is a silvery cloud in the front of feathers or fibres seen high up against a blue sky.
单项选择题 （）are mainly caused by the gravitational pull of the moon.
单项选择题 （）generally indicates that a gale or storm is approaching.
