单项选择题
An occluded front on a weather map is colored（）.
A.blue line B.purple line C.dashed blue line D.alternate red and blue line
单项选择题 An aneroid barometer is an instrument（）.
单项选择题 An air mass is termed warm if（）.
单项选择题 All of the following are associated with cumulonimbus clouds EXCEPT（）.
