单项选择题
Fog forms when the air（）.
A.Is 50% water saturated B.Is 90% water saturated C.Temperature is greater than the dew point temperature D.Temperature is equal to，or below the dew point temperature
单项选择题 Fetch is the（）.
单项选择题 Cyclones that have warm sectors usually move（）.
单项选择题 Cumulus clouds that have undergone vertical development and have become cumulonimbus in form，indicate（）.
