单项选择题
In a microbarograph，the pen should be checked and the ink well filled（）.
A.each time the chart is changed B.once per month C.once per week D.daily
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（）.
单项选择题 Cumulonimbus clouds can produce（）.
