单项选择题
Two well-developed high pressure areas may be separated by a（）.
A.Hill of low pressure B.Trough of low pressure C.Valley of low pressure D.Ridge of low pressure
单项选择题 Tropical cyclones are classified by form and intensity.Which system does not have closed isobars（）.
单项选择题 The wind is（）and decreasing.
单项选择题 The strong wind will make us（）here for some days.
