单项选择题
A hygrometer is a device used for determining（）.
A.the absolute temperature B.atmospheric pressure C.wind velocity D.relative humidity
单项选择题 A generally circular low pressure area is called a(n)（）.
单项选择题 A frontal thunderstorm is caused by（）.
单项选择题 A cyclone in its final stage of development is called a(n)（）.
