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Floods, storms and other natural events kill thousands of people every year. So does extreme heat. Experts say heat may be nature’s deadliest killer. For example, extreme heat was blamed for killing more than one hundred people in India and Pakistan in two thousand seven. Daytime temperatures rose to more than forty-five degrees Celsius in some areas. On June eleventh, the temperature in one desert town hit fifty-one degrees.
Experts say the total heat of a hot day or several days can affect health. Several hot days are considered a heat wave. Experts say heat waves often become dangerous when the nighttime temperature does not drop much from the highest daytime temperature. This causes great stress on the human body.
Doctors say people can do many things to protect themselves from the dangers of extreme heat. Stay out of the sun, if possible. Drink lots of cool water. Wear light colored clothing made of natural materials. Make sure the clothing is loose, pe
A. The total heat of a hot day or several days can not affect health.
B. People can not do any things to protect themselves from the dangers of extreme heat.
C. The most common health problem caused by hot weather is heat stress.
D. Humidity is the amount of water in the room.

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Floods, storms and other natural events kill thousands of people every year. So does extreme heat. Experts say heat may be nature’s deadliest killer. For example, extreme heat was blamed for killing more than one hundred people in India and Pakistan in two thousand seven. Daytime temperatures rose to more than forty-five degrees Celsius in some areas. On June eleventh, the temperature in one desert town hit fifty-one degrees.
Experts say the total heat of a hot day or several days can affect health. Several hot days are considered a heat wave. Experts say heat waves often become dangerous when the nighttime temperature does not drop much from the highest daytime temperature. This causes great stress on the human body.
Doctors say people can do many things to protect themselves from the dangers of extreme heat. Stay out of the sun, if possible. Drink lots of cool water. Wear light colored clothing made of natural materials. Make sure the clothing is loose, pe
A. Floods.
B. Storms.
C. Extreme heat.
D. Lack of water.

[单项选择]People kill each other over diamonds; countries go to war over oil. But the world’s most expensive commodities are worth nothing in the absence of water. Fresh water is essential for life, with no substitute. Although mostly unpriced, it is the most valuable stuff in the world.
Nature has decided that the supply of water is fixed. Meanwhile demand rises as the world’s population increases and enriches itself Homes, factories and offices are sucking up ever more. But it is the planet’s growing need for food that matters most. Farming accounts for 70% of withdrawals.
Few of the world’s great rivers that run through grain-growing areas now reach the sea all the year round or, if they do, they do so as a trickle. Less obvious, though even more serious, are the withdrawals from underground, which are hidden from sight but big enough to produce changes in the Earth’s gravitational field that can be monitored by NASA’s satellites in space. Water tables are now falling in many parts
A. The value of diamonds and oil is much less than that of water.
B. Fresh water is indispensable to human because nothing can take its place.
C. It is hard to price the value of water, because it is too valuable.
D. Water is priceless because the world is always in the absence of it.

[单项选择] What Are Tropical Storms Severe storms spawned in the tropics are known by different names in different parts of the world: hurricanes in the Atlantic and east Pacific and typhoons in the northwest Pacific and cyclones in the southwest Pacific and Indian Ocean. These storms originate over tropical waters, close to the equator. If the atmosphere is calm and the water is warmer than about 27°C, evaporation forces large amounts of moisture into the air, creating a low pressure system. When this water vapor condenses, it releases heat that powers the circular winds that characterize these storms. Rainfall in the developing storm releases more heat, triggering a convection process that pulls more moisture-laden air up through the centre of the system. The storm grows via this feedback mechanism. The strongest winds are found immediately outside the centre, or "eye," of the hurricane at ground level. Every one of these systems begins as a trop
A. Y
B. N
C. NG