单项选择题
Cumulonimbus clouds can produce（）.
A.dense fog and high humidity B.gusty winds，thunder，rain or hail，and lightning C.clear skies with the approach of a cold front D.a rapid drop in barometric pressure followed by darkness
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（）.
单项选择题 Clouds are classified according to their（）.
