【单选题】{{B}}第三篇{{/B}}
Hurricane (飓风) Katrina
A、hurricane is a fiercely powerful, rotating(旋转的)form of tropical storm that can be 124 to 1,240 miles in diameter. The term hurricane is derived from Hurican, the name of a nativeAmerican storm goD、Hurricanes are typical of a calm central region of low pressure between "12 to 60 miles in diameter, known as the eye. They occur in tropical regions. Over its lifetime, one of these can release as much energy as 10,000 nuclear bombs.
The seed for hurricane formation is a cluster(聚集) of thunderstorm over warm tropical waters. Hurricanes can only form and be fed when the sea-surface temperature exceeds 27℃ and the surrounding atmosphere is calm. These requirements are met between June and November in the northern part of the worlD、
Under these conditions, large quantities of water evaporate (蒸发) and condense (冷凝) into clouds and rain-releasing heat in the process. It is this heat energy, combined with the rotation of theEarth, that drives a hurricane.
When the warm column of air from the sea surface first begins to rise, it causes an area of low pressure. This in turn creates wind as air is drawn into the areA、This spinning wind drags up more moist air from the sea surface in a process that strengthens the storm.Cold air falls back to the ocean surface through the eye and on the outside of the storm.
Initially, when wind speeds reach 23 miles per hour, these mild, wet and grey weather systems are known as depressions, or low air pressure. Hurricane Katrina formed in this way over the southeasternBahamas on 23August 2005, Katrina has had a devastating impact on the GulfCoast of the US, leaving a disaster zone of 90,000 square miles in its wake(尾迹)-almost the size of the UK. Thousands have been killed or injured and more than half a million people have become homeless in a humanitarian(人道主义的) crisis of a scale not seen in the US since the GreatDepression. The cost of the damage may top $100 billion.
B．High air pressure.
C．Warm sea-surface temperature.
D．A、group of thunderstorms over warm tropical waters.
网考网参考答案：A
网考网解析：
[解析] 第二段的第一、二句描写飓风的形成原因，最后一句中的These requirements即是第一、二句中所述内容。所以B、C和D都不是正确选项。 document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>
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