单项选择题
Steam fog is most likely to occur on the Mississippi and Ohio Rivers in（）.
A.spring，around late evening B.spring，around early evening C.fall，around early morning D.fall，around midday
单项选择题 Radiation fog（）.
单项选择题 On the pole side of the trade wind belt，there is an area of high pressure with weak pressure gradients and light，variable winds. This area is called the（）.
单项选择题 Ocean currents are well defined and（）.
