单项选择题
Fetch is the（）.
A.Distance a wave travels between formation and decay B.Stretch of water over which a wave-forming wind blows C.Time in seconds required for two crests to pass a given point D.Measurement of a wave's steepness
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（）.
单项选择题 Cumulonimbus clouds are formed by（）.
