单项选择题
A.air being warmed above the dew point
B.saturation of cold air by rain
C.a rapid cooling of the air near the surface of the Earth at night
D.warm moist air being blown over a colder surface
单项选择题 Advection fog holds longest over which portions of the lakes?（）
单项选择题 A tide is called diurnal when（）.
单项选择题 A swift current occurring in a narrow passage connecting two large bodies of water which is produced by the continuously changing difference in height of tide at the two ends of the passage is called a(n)（）.