Against the supposition（假设）that forest fires in Alaska, Canada and Siberia warm the climate, scientists have discovered that cooling may occur in areas where burnt trees allow more snow to mirror more sunlight into space.

    This finding suggests that taking steps to prevent northern forest to limit the release of greenhouse gases may warm the climate in northern regions. Usually large fires destroyed forests in these areas over the past decade. Scientists predict that with climate warming, fires may occur more frequently over next several centuries as a result of a longer fire season. Sunlight taken in by the earth tends to cause warming, while heat mirrored back into space tends to cause cooling.

    This is the first study to analyze all aspects of how northern fires influence climate. Earlier studies by other scientists have suggested that fire in northern regions speed up climate warming because greenhouse gases from burning trees and plants are released into the atmosphere and thus trap heat.

    Scientists found that right after the fire, large amounts of greenhouse gases entered the atmosphere and caused warming. Ozone（臭氧）levels increased, and ash from the fire fell on far-off sea ice, darkening the surface and causing more radiation from the sun to be taken in. The following spring, however, the land within the area of the fire was brighter than before the fire, because fewer trees covered the ground. Snow on the ground mirrored more sunlight back into space, leading to cooling.

    “We need to find out all possible ways to reduce the growth of greenhouse gases in the atmosphere.” Scientists tracked the change in amount of radiation entering and leaving the climate system as a result of the fire, and found a measurement closely related to the global air temperature. Typically, fire in northern regions occurs in the same area every 80 to 150 years. Scientists, however, found that when fire occurs more frequently, more radiation is lost from the earth and cooling results. Specifically, they determined when fire returns 20 years earlier than predicated, 0.5 watts per square meter of area burned are soaked up by the earth from greenhouse gases, but 0.9 watts per square meter will be sent back into space. The net effect is cooling. Watts are used to measure the rate at which energy is gained or lost from the earth.

1.According to the new findings, taking steps to prevent northern forest fires may _______.

    A. result in a warming climate

    B. cause the forest fires to occur more frequently

    C. lead to a longer fire season

    D. protect the forests and the environment there

2. The following are all the immediate effects after a forest fire EXCEPT _________.

    A. large amounts of greenhouse gases enter the atmosphere

    B. the levels of ozone which is a type of oxygen increase

    C. snow on the ground mirrors more sunlight back into space

    D. ashes from the fire fall on the ice surface and take in more radiation from the sun

3.Earlier studies about northern forest fires _________.

    A. analyze all aspects of how northern fires influence climate

    B. indicate that forest fires will pollute the atmosphere

    C. suggest that people should take measures to protect environment

    D. suggest that the fires will speed up climate warming

4.The underlined part “soaked up” in the last paragraph most probably means ________.

    A. released       B. absorbed       C. created        D. distributed

5.From the passage we can draw a conclusion that forest fires in Alaska, Canada and Siberia may __________.

    A. warm the climate as the supposition goes

    B. allow more snow to reflect more sunlight into space and thus cool the climate

    C. destroy large areas of forests and pollute the far-off sea ice

    D. help to gain more energy rather than release more energy

Scientists in Israel have discovered a new way to test for water pollution by "listening" to what the plants growing in water have to say．By shining a laser beam(激光束) on the tiny pieces of algae(海藻) floating in the water, the researchers said they hear sound waves that tell them the type and amount of pollution in the water．

"It is a red light, telling us that something is beginning to go wrong with the quality of water," said Zvy Dubinsky, an aquatic biologist at Israel's Bar Ilan University．"Algae is the first thing to be affected by a change in water quality．"

As water sources deteriorate worldwide, the testing of algae could be used to monitor water quality faster, more cheaply and more accurately than techniques now in use, Dubinsky said．The secret is to measure the rate of photosynthesis(光合作用) in the algae, meaning the plant's ability to transform light into energy．During photosynthesis, plants also release oxygen into the air．

Dubinsky's technique is easy to perform because of the over-abundance of algae in the planet's water．Most of the oxygen in the atmosphere comes from algae．A prototype tester shoots a laser beam at water samples to stimulate photosynthesis in the algae．But not all of the laser's heat is used．

Depending on the condition of the algae and the rate of photosynthesis, some of the heat is shot back into the water, creating sound waves, Dubinsky said．With a special underwater microphone, researchers are able to analyze the strength of the sound waves and determine the health of the algae and the condition of the surrounding water．

"Algae suffering from lead poisoning, like waste discharged from battery and paint manufacturing plants, will produce a different sound than those suffering from lack of iron or exposure to other toxins," said researcher Yulia Pinchasov．

72．To study water quality, scientists choose algae mainly because        ．

A．algae is most easily affected by pollution

B．most oxygen is produced by algae

C．the amount of algae is decreasing

D．algae is a kind of plant floating in the water

73．When Dubinsky studied water quality, he mainly focused on        ．

A．the amount of laser used by algae

B．the rate of photosynthesis in the algae

C．the condition of the algae

D．the heat of laser used by algae

74．After the study, scientists proved that        ．

A．the increase in population is caused by lack of water

B．global warming causes water resources to reduce worldwide

C．algae can show the type and amount of pollution in the water

D．algae is dying out in the ocean around the world

75．What would be the most suitable title for the passage?

A．Water pollution is reduced with the growth of algae

B．Pollution makes it hard for plants to make photosynthesis

C．Water pollution affects the growth of marine plants

D．Scientists listen to plants to find pollution

    As bananas ripen， the green skin turns ye11ow gradually. Chemical changes occur in the f1esh of the fruit as well：starch（淀粉）changes to sugar；pectin（果胶）breaks down，losing its stiffness； and the f1esh softens.

Is ripening fruit a self－contained system， or is the rate of these changes affected by the environment？ We designed the experiment below to see if different atmospheres， produced by different packaging， affected the rate of ripening. You will vary the atmosphere surrounding unripe bananas and observe the effect on the ripening process。

Now set up the bananas in their environments as follows：

1. Put two green bananas in a paper bag and fo1d the top over to seal out the air.

2．Put one green banana and the very ripe banana in the other paper bag and fold over the top.

3. Put two green bananas in a plastic bag and seal it.

4. Wrap（包）one green banana tightly in a plastic bag.

5. Leave one green banana exposed to the air.

Leave the fruit a1one or five days to ripen. Ripening fruit“breathes”． This means that it takes up oxygen and gives off C02. Oxygen is extremely important and necessary for the chemical reactions involved in ripening. In addition, ripening fruit gives off another gas, called ethylene（乙烯）. Not only is ethylene a product of ripening fruit, it also promotes the further ripening of the fruit.

Paper bags tend to keep the ethylene in, but they allow oxygen and ethylene to pass through slowly. Plastic bags do not allow the free flow of oxygen or ethylene. In this experiment, the green banana in paper bag with the ripe banana should ripen most quickly. The green bananas in the paper bag should ripen faster than the bananas in the plastic bag. The banana left exposed to air has an unlimited supply of oxygen, so it will turn brown most quickly. You will notice that the side of this banana that rests on the counter will ripen more quickly than the other sides, because it has the

closest contact（接触）with its own ethylene. The banana that is tightly wrapped in plastic has no oxygen supply and should ripen most slowly. Now can you see why bananas are sealed in plastic in many supermarkets？

72. What makes the green banana in Bag 2 ripen more quickly than the ones in Bag 1？

A. Ethylene from the very ripe banana.            B. The free flow of oxygen or ethylene

C. C02 from the very ripe banana.                     D. The limitation of oxygen supply.

73. How can we slow down the ripening of bananas exposed to the air？

A. To rest them on the counter.                                   B. To keep them in the basket.

C. To put them on the ground.                                     D. To hang them up from the ceiling

74. It can be concluded from the passage that          .

A. the ripening banana is a self-contained system

B. the rate of ripening bananas is affected by the environment

C. wrapped bananas experience no chemical changes to ripen

D. ripening bananas give off oxygen, C0, and ethylene

75. Why are bananas sealed in plastic in many supermarkets？

A. To make them ripen more quickly.                B. To make them ripen more slowly.

C. To make banana flesh soften.                        D. To turn green bananas yellow.

III．阅读理解（满分50分）
　　阅读下面短文，从每题所给的A、B、C和D项中选出最佳选项，并在答题卡上将该项涂黑。
A
Against the supposition that forest fires in Alaska, Canada and Siberia warm the climate, scientists have discovered that cooling may occur in areas where burnt trees allow more snow to mirror more sunlight into space.
This finding suggests that taking steps to prevent northern forest fires to limit the release of greenhouse gases may warm the climate in northern regions. Usually large fires destroyed forests in these areas over the past decade. Scientists predict that with climate warming, fires may occur more frequently over the next several centuries as a result of a longer fire season. Sunlight taken in by the earth tends to cause warming, while heat mirrored back into space tends to cause cooling.
This is the first study to analyze all aspects of how northern fires influence climate. Earlier studies by other scientists have suggested that fire in northern regions speed up climate warming because greenhouse gases from burning trees and plants are released into the atmosphere and thus trap heat.
Scientists found that right after the fire, large amounts of greenhouse gases entered the atmosphere and caused warming. Ozone（臭氧） levels increased, and ash from the fire fell on far-off sea ice, darkening the surface and causing more radiation from the sun to be taken in. The following spring, however, the land within the area of the fire was brighter than before the fire, because fewer trees covered the ground. Snow on the ground mirrored more sunlight back into space, leading to cooling.
“We need to find out all possible ways to reduce the growth of greenhouse gases in the atmosphere.” Scientists tracked the change in the amount of radiation entering and leaving the climate system as a result of the fire, and found a measurement closely related to the global air temperature. Typically, fire in northern regions occurs in the same area every 80 to 150 years. Scientists, however, found that when fire occurs more frequently, more radiation is lost from the earth and cooling results. Specifically, they determined when fire returns 20 years earlier than predicted, 0.5 watts per square meter of area burned are soaked up by the earth from greenhouse gases, but 0.9 watts per square meter will be sent back into space. The net effect is cooling. Watts are used to measure the rate at which energy is gained or lost from the earth.
41. According to the new findings, taking steps to prevent northern forest fires may __________.
A. result in a warming climate          
B. cause the forest fires to occur more frequently
C. lead to a longer fire season            
D. protect the forests and the environment there
42. The following are all the immediate effects after a forest fire EXCEPT __________.
A. large amounts of greenhouse gases enter the atmosphere
B. the levels of ozone which is a type of oxygen increase
C. snow on the ground mirrors more sunlight back into space
D. ashes from the fire fall on the ice surface and take in more radiation from the sun
43. Earlier studies about northern forest fires __________.
A. analyze all aspects of how northern fires influence climate
B. indicate that forest fires will pollute the atmosphere
C. suggest that people should take measures to protect environment
D. suggest that the fires will speed up climate warming
44.The underlined phrase “soak up” in the last paragraph most probably means __________.
A. released         B. absorbed       C. created      D. distributed
45. From the passage we can draw a conclusion that forest fires in Alaska, Canada and Siberia may __________.
A. warm the climate as the supposition goes
B. allow more snow to reflect more sunlight into space and thus cool the climate
C. destroy large areas of forests and pollute the far-off sea ice
D. help to gain more energy rather than release more energy

Against the supposition that forest fires in Alaska, Canada and Siberia warm the climate, scientists have discovered that cooling may occur in areas where burnt trees allow more snow to mirror more sunlight into space.

    This finding suggests that taking steps to prevent northern forest fires to limit the release of greenhouse gases may warm the climate in northern regions. Usually large fires destroyed forests in these areas over the past decade. Scientists predict that with climate warming, fires may occur more frequently over the next several centuries as a result of a longer fire season. Sunlight taken in by the earth tends to cause warming, while heat mirrored back into space tends to cause cooling.

    This is the first study to analyze all aspects of how northern fires influence climate. Earlier studies by other scientists have suggested that fire in northern regions speed up climate warming because greenhouse gases from burning trees and plants are released into the atmosphere and thus trap heat.

    Scientists found that right after the fire, large amounts of greenhouse gases entered the atmosphere and caused warming. Ozone（臭氧） levels increased, and ash from the fire fell on far-off sea ice, darkening the surface and causing more radiation from the sun to be taken in. The following spring, however, the land within the area of the fire was brighter than before the fire, because fewer trees covered the ground. Snow on the ground mirrored more sunlight back into space, leading to cooling.

    “We need to find out all possible ways to reduce the growth of greenhouse gases in the atmosphere.” Scientists tracked the change in the amount of radiation entering and leaving the climate system as a result of the fire, and found a measurement closely related to the global air temperature. Typically, fire in northern regions occurs in the same area every 80 to 150 years. Scientists, however, found that when fire occurs more frequently, more radiation is lost from the earth and cooling results. Specifically, they determined when fire returns 20 years earlier than predicted, 0.5 watts per square meter of area burned are soaked up by the earth from greenhouse gases, but 0.9 watts per square meter will be sent back into space. The net effect is cooling. Watts are used to measure the rate at which energy is gained or lost from the earth.

46. According to the new findings, taking steps to prevent northern forest fires may __________.

A. result in a warming climate     

B. cause the forest fires to occur more frequently

C. lead to a longer fire season             

D. protect the forests and the environment there

47. The following are all the immediate effects after a forest fire EXCEPT __________.

A. large amounts of greenhouse gases enter the atmosphere

B. the levels of ozone which is a type of oxygen increase

C. snow on the ground mirrors more sunlight back into space

D. ashes from the fire fall on the ice surface and take in more radiation from the sun

48. Earlier studies about northern forest fires __________.

A. analyze all aspects of how northern fires influence climate

B. indicate that forest fires will pollute the atmosphere

C. suggest that people should take measures to protect environment

D. suggest that the fires will speed up climate warming

49.The underlined phrase “soak up” in the last paragraph most probably means __________.

A. released         B. absorbed       C. created      D. distributed

50. From the passage we can draw a conclusion that forest fires in Alaska, Canada and Siberia may __________.

A. warm the climate as the supposition goes

B. allow more snow to reflect more sunlight into space and thus cool the climate

C. destroy large areas of forests and pollute the far-off sea ice

D. help to gain more energy rather than release more energy