单项选择题
An occluded front is caused by a(n)（）.
A.low pressure area B.high pressure area C.area of calm air D.cold front overtaking a warm front
单项选择题 An instrument designed to maintain a continuous record of atmospheric pressure is a(n)（）.
单项选择题 An atoll cloud forming over an island due to heating of the land during the daytime would be which type? （）
单项选择题 Advection fog is most commonly caused by（）.
