单项选择题
During a period of whiteout，you should expect which of the following（）.
A.Snowfall or blowing snow
B.Lack of ability to estimate distance
C.Harsh contrast between sun-illuminated snow cover and the background
D.Hazy horizons with extensive mirage effects
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相关考题
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单项选择题
Due to lapse of time the risk in these areas to surface navigation is now considered （）than the ordinary risks of navigation，but a very real risk still exists with regard to anchoring，fishing or any form of submarine or seabed activity.
A.more serious
B.not less serious
C.more dangerous
D.no more dangerous -
单项选择题
Conditions for crossing a rough bar are usually best at （）.
A.low water slack
B.high water slack
C.high water ebb
D.high water flood -
单项选择题
Clearances of bridges and overhead cables below Bonneville Dam refer to heights in feet above mean （）.
A.lower low water
B.high water
C.low water
D.sea level
