单项选择题
A frontal thunderstorm is caused by（）.
A.pronounced local heating B.wind being pushed up a mountain C.a warm air mass rising over a cold air mass D.an increased lapse rate caused by advection of warm surface air
单项选择题 A cyclone in its final stage of development is called a(n)（）.
单项选择题 A cloud sequence of cirrus，cirrostratus，and altostratus clouds followed by rain usually signifies the approach of a(n)（）.
单项选择题 A cloud of marked vertical development (often anvil-shaped) would be classified as（）.
