Trees are useful to man in three important ways: they provide him with wood and other products; they give him shade; and they help to prevent droughts and floods.
Unfortunately, in many parts of the world, man has not realized that the third of these services is the most important. (78)In his eagerness to make money from trees, he has cut them down in large numbers, only to find that without them he has lost the best friends he bad. And besides, be is usually too careless to plant and look after new trees. So the forests slowly disappear.
This does not only mean that man will have fewer trees. The results are even more serious: for where there are trees, their roots break up soil—allowing the rain to sink in—and also bind the soil, thus preventing it from being washed away easily; but where there are no trees, the rain falls on hard ground and flows away, causing floods and carrying away the rich top-soil. When all the top-soil is gone, nothing remains but worthless desert.
Two thousand years ago a rich and powerful country cut down its trees to build warships, with which to gain itself an empire. It set up the empire but, without its trees, its soil became poor and it grew weak. When the empire fell to pieces, the home country found itself faced with floods and starvation.
Why does land become desert after all trees are cut down

A:Because nothing remains on land except floods. B:Because there are no longer trees to keep the rain and protect the top-soil. C:Because too much rain sinks in and washes away the top-soil. D:Because roots of the trees break up the soil.

Passage Two
Thousands of years ago, in the middle of an ocean, miles from the nearest island, an undersea volcano(火山) broke out. The hot liquid rock piled higher and higher and spread wider and wider. In this way, an island rose up in the sea.
As time went on, hot sun and cool rains made the rock split and break to pieces. Sea waves dashed against the rock. In this way, soil and sand came into being.
Nothing lived on the naked soil. And then the wind and birds brought plant seeds, spiders and other little creatures there. Only plants could grow first. Only they, in sunlight, could produce food from the minerals of the soil, water and air. While many animals landed on the island, they could find no food. A spider spun its web in vain, because there were no insects for its web to catch, In sects couldn’ t stay until there were plants for them to eat. So plants had to be the pioneer life on this new island.

The order of coming into being on the island is（）

A:soil, plants and animals                    B:soil, little creatures and plants C:C．soil, birds and plants         D:soil, human beings and animals

Passage 2

Why does land become desert after all trees are cut down

A:Because nothing remains on land except floods. B:Because there are no longer trees to keep the rain and protect the top-soil. C:Because too much rain sinks in and washes away the top-soil. D:Because roots of the trees break up the soil.

Passage Two Thousands of years ago, in the middle of an ocean, miles from the nearest island, an undersea volcano(火山) broke out. The hot liquid rock piled higher and higher and spread wider and wider. In this way, an island rose up in the sea. As time went on, hot sun and cool rains made the rock split and break to pieces. Sea waves dashed against the rock. In this way, soil and sand came into being. Nothing lived on the naked soil. And then the wind and birds brought plant seeds, spiders and other little creatures there. Only plants could grow first. Only they, in sunlight, could produce food from the minerals of the soil, water and air. While many animals landed on the island, they could find no food. A spider spun its web in vain, because there were no insects for its web to catch, In sects couldn’ t stay until there were plants for them to eat. So plants had to be the pioneer life on this new island.

The order of coming into being on the island is （）

A:soil, plants and animals                    B:soil, little creatures and plants C:C．soil, birds and plants                     D:soil, human beings and animals

Passage 3

What does a new gardener usually decide to do to keep their potted plants alive ______.

A:Underwatering the plants B:Fertilising the pot soil C:Overwatering the plants D:Loosing the pot soil

Plant Gas
Scientists have been studying natural sources of methane for decades but hadn’t regarded plants as a producer, notes Frank Keppler, a geochemist at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. Now Keppler and his colleagues find that plants, from grasses to trees, may also be sources of the greenhouse gas. This is really surprising, because most scientists assumed that methane production requires an oxygen-free environment.
Previously, researchers had thought that it was impossible for plants to make significant mounts of the gas. They had assumed that microbes need to be in environments without oxygen to produce methane. Methane is a greenhouse gas, like carbon dioxide. Gases such as methane and carbon dioxide trap heat in Earth’s atmosphere and contribute to global warming.
In its experiments, Keppler’s team used sealed chambers that contained the same concentration of oxygen that Earth’s atmosphere has. They measured the amounts of methane that were released by both living plants and dried plant material, such as fallen leaves.
With the dried plants, the researchers took measurement at temperatures ranging from 30 degrees Celsius to 70 degrees C. At 30 degrees C, they found, a gram of dried plant material released up to 3 nanograms of methane per hour. ( One nanogram is a billionth of a gram. ) With every 10-degree rise in temperature, the amount of methane released each hour roughly doubled.
Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour. Methane emissions tripled when living and dead plant was exposed to sunlight.
Because there was plenty of oxygen available, it’s unlikely that the types of bacteria that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions. That’s another strong sign that the gas came from the plants and not soil microbes.
The new finding is an "interesting observation," says Jennifer Y. King, a biogeochemist at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane, they may prevent plant-produced methane from reaching the atmosphere. Field tests will be needed to assess the plant’s influence, she notes.

Which of the following about methane is Not mentioned in the passage（　）

A:Plants growing in soil release methane. B:Plants growing in water release methane. C:Soil microbes consume methane. D:Microbes in plants produce methane.

{{B}}第二篇{{/B}}

What was discovered by NASA’s Phoenix Mars Lander on Mars?

A:Vast lakes. B:Flowing rivers. C:Water in a soil sample. D:Living things.

{{B}}第三篇{{/B}}

Which of the following about methane is Not mentioned in the passage?

A:Plants growing in soil release methane. B:Plants growing in water release methane. C:Soil microbes consume methane. D:Microbes in plants produce methane.

Scientists have been studying natural sources of methane for decades but hadn’t regarded plants as a producer, notes Frank Keppler, a geochemist at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. Now Keppler and his colleagues find that plants, from grasses to trees, may also be sources of the greenhouse gas. This is really surprising, because most scientists assumed that methane production requires an oxygen-free environment.
Previously, researchers had thought that it was impossible for plants to make significant amounts of the gas. They had assumed that microbes need to be in environments without oxygen to produce methane. Methane is a greenhouse gas, like carbon dioxide. Gases such as methane and carbon dioxide trap heat in Earth’s atmosphere and contribute to global warming.
In its experiments, Keppler’s team used sealed chambers that contained the same concentration of oxygen that Earth’s atmosphere has. They measured the amounts of methane that were released by both living plants and dried plant material, such as fallen leaves.
With the dried plants, the researchers took measurement at temperatures ranging from 30 degrees Celsius to 70 degrees. At 30 degrees, they found, a gram of dried plant material released up to 3 nanograms of methane per hour. (One nanogram is a billionth of a gram.) With every 10-degree rise in temperature, the amount of methane released each hour roughly doubled.
Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour. Methane emissions tripled when living and dead plant was exposed to sunlight.
Because there was plenty of oxygen available, it’s unlikely that the types of bacteria that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions. That’s another strong sign that the gas came from the plants and not soil microbes.
The new finding is an "interesting observation," says Jennifer Y. King, a biogeochemist at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane, they may prevent plant-produced methane from reaching the atmosphere. Field tests will be needed to assess the plant’s influence, she notes.
What of the following about methane is Not mentioned in the passage

A:Plants growing in soil release methane. B:Plants growing in water release methane. C:Soil microbes consume methane. D:Microbes in plants produce methan