单项选择题
Cyclones tend to move（）.
A.perpendicular to the isobars in their warm sectors B.parallel to the isobars in their warm sectors C.parallel to the line of the cold front D.perpendicular to the line of the cold front
单项选择题 Cumulonimbus clouds can produce（）.
单项选择题 Cumulonimbus clouds are most likely to accompany a(n)（）.
单项选择题 Clouds that form as small white flakes or scaly globular masses covering either small or large portions of the sky are（）.
