单项选择题
Altocumulus clouds are defined as（）.
A.high clouds B.middle clouds C.low clouds D.vertical development clouds
单项选择题 Above-normal tides near the center of a hurricane maybe caused by the（）.
单项选择题 A very light breeze that causes ripples on a small area of still water is a（）.
单项选择题 A thin，whitish，high cloud popularly known as mares tails is（）.
