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
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相关考题
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单项选择题
If an observer in the Northern Hemisphere faces the surface wind，the center of low pressure is to his（）.
A.left，slightly behind him
B.right，slightly behind him
C.left，slightly in front of him
D.right，slightly in front of him -
单项选择题
Cyclones tend to move（）.
A.perpendicular to the isobars in their warm sectors
B.parallel to the isobars in their warm sectors
C.parallel to the line of the cold front
D.perpendicular to the line of the cold front -
单项选择题
Cumulonimbus clouds can produce（）.
A.dense fog and high humidity
B.gusty winds，thunder，rain or hail，and lightning
C.clear skies with the approach of a cold front
D.a rapid drop in barometric pressure followed by darkness
