If the current and wind are in opposite directions，the sea surface represents ______.A.a greatly reduced wind speedB.a higher wind speed than what really existsC.a lower wind speed than what really existsD.more turbulent winds

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第二篇

Hurricane（咫风）Katrina

A hurricane is a fiercely powertul , 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
native American 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 storms can release as much energy as 10,000 nuclear
bombs.
The seed for hurricane formation is a cluster（聚集）of thunderstorms 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 the Earth,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 south-eastern Bahamas on 23 August 2005.Katrina has had a devastating
impact on the Gulf Coast of the US,leaving a disaster zone of 90,000 square miles in its
wake（尾迹）一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 Great Depression.The cost of the damage may top
$100 billion.

When the warm air from the sea surface begins to rise,it
A:creates an area of low pressure.
B:supplies cold air to the eye of a hurricane.
C:increases the sea-surface temperature.
D:strengthens the rotation of the earth.