单项选择题
In many areas atoll clouds (clouds of vertical development) are produced over small islands. These are the result of（）.
A.rising air currents produced by the warm islands B.warm air from the sea rising over higher land areas C.cool land air mixing with warm sea air D.descending air over the islands
单项选择题 In a microbarograph，the pen should be checked and the ink well filled（）.
单项选择题 If an observer in the Northern Hemisphere faces the surface wind，the center of low pressure is to his（）.
单项选择题 Cyclones tend to move（）.
