单项选择题
A single barometric pressure reading of 28.60 indicates（）.
A.rapidly improving weather B.deteriorating weather C.a severe low pressure system D.fair weather and calm
单项选择题 A signal indicating zone time is preceded with the letter（）.
单项选择题 A signal indicating Greenwich mean time would be preceded with（）.
单项选择题 A sign of thunderstorm development is a cumulus cloud（）.
