（）forms over land，most frequently during autumn and winter over low-lying land，especially if it is damp and marshy and in valleys on quiet nights with clear skies.

单项选择题（） blow more or less constantly（except when monsoons prevail）throughout all seasons at a mean speed of around 14 knots and are generally strongest in the late winter.

A.Trade Winds
B.Winds of the temperate zones
C.Monsoons
D.Land and Sea Breezes

单项选择题（）are experienced in temperate latitudes during warn summer weather but rarely exceed Force 3 and may extend 10 to 15 miles on either side of the coastline.

A.Trade Winds
B.Winds of the temperate zones
C.Monsoons
D.Land and Sea Breezes

单项选择题Steady precipitation is typical of（）.

A.coming cold weather conditions
B.a warm front weather condition
C.high pressure conditions
D.scattered cumulus clouds

单项选择题Snow has obliterated surface features and the sky is covered with uniform，altostratus clouds. There are no shadows and the horizon has disappeared. What is this condition called? （）

A.Ice blink
B.Whiteout
C.Water sky
D.Aurora reflection

单项选择题Relative humidity is the percentage of water vapor that is in the air as compared to the maximum amount it can hold at（）.

A.a specific barometric pressure
B.a specific temperature
C.a specific wind speed
D.any time