单项选择题
As a cold front passes an observer，pressure（）.
A.drops and winds become variable B.rises and winds become gusty C.drops and winds become gusty D.rises and winds become variable
单项选择题 An occluded front is usually caused by a（）.
单项选择题 An occluded front is caused by a(n)（）.
单项选择题 An instrument designed to maintain a continuous record of atmospheric pressure is a(n)（）.
