单项选择题
The apparent wind can be zero when the true wind is from（）.
A.ahead and equal to the ship's speed B.astern and equal to the ship's speed C.ahead and equal to twice the ship's speed D.astern and equal to twice the ship's speed
单项选择题 Steam fog is most likely to occur on the Mississippi and Ohio Rivers in（）.
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（）.
