Weather changes when the temperature and the amount of water in the atmosphere change. We can see and feel water coming from the atmosphere when we have rain. But the water must somehow get back to the atmosphere. Meteorologists call this the water cycle.

   There are many stages in the water cycle. Rain falls when water vapour in clouds condenses(凝结). Drops of water form and fall to the ground. The water soaks into the ground and feeds streams and rivers. A lot of rain falls into the sea. The heat of the sun evaporates some of the water in the ground and in the rivers, lakes, and the sea. It changes the liquid water into water vapour. The vapour rises onto the air. Water vapour is normally invisible. On a very damp or humid day, however, you can sometimes see water vapour rising from a puddle(水坑) or pond in a mist(薄雾) above the water. Water vapour also gets into the air from living things. Trees and other plants take in water through their roots and give off water vapour from their leaves. People and land animals drink water and breathe out water vapour. In all these ways the water returns to the air. There it gathers to form clouds and condenses to form rain. The rain falls to earth, and the cycle starts again. It continues even if snow or hail(冰雹) fall instead because both eventually melt to form water. The amount of water vapour in the air depends on the temperature. The air is more moist(潮湿) in the tropics(热带) than in the cold polar regions.

What is the main idea of the passage?

A. Water cycle.    B. Water vapour. C. How rain forms.   D.Water, vapour, rain.

How many ways of the water returning to the air are discussed in the text?

A. Two.   B. Three.   C. Four.     D. Five.

Whether water vapour can be seen or not depends on _______.

A. how much water is evaporated         B. how good your eyes are

C. in which way water is evaporated           D. climate or weather

From the passage we get to know _______.

A. there is more water vapour in the air in the tropics than in cold polar regions

B. there is more water vapour in the air in cold polar region than in the tropics

C. it gets more rain in the tropics than in cold polar regions because there is less vapour

D. the amount of water vapour in the air depends on how often it rains

ABCD请按实际情况填写。其他请参照下表填写。

A, B, C, D, E(AB), F(AC)

1.

While everybody enjoys fresh cut flowers around his house, few people know how to keep them for as long as possible. This may be done by keeping in mind a few simple facts. The key to keeping fresh cut flowers for a week or more without floral preservatives(which contain biocides that kill bacteria and fungus) is to keep the water fresh and the stems free of air pockets so they can continue to draw up water.

2.

An important thing to remember about cut flowers is that they are sensitive to temperature. For example, studies have shown that cut carnations(康乃馨) retain their freshness eight times longer when kept at 12℃ than when kept at 26℃. Keeping freshly harvested flowers at the right temperatures is probably the most important aspect of flower care.

3.

Flowers are not intended by nature to live very long. Their biological purpose is simply to attract birds or insects, such as bees, for pollination (授粉). After that, they quickly dry up and die. The process by which flowers consume oxygen and produce carbon dioxide, called respiration (呼吸), generates the energy the flower needs to give the flower its shape and colour. The making of seeds also depends on this energy. While all living things respire, flowers have a high level of respiration. A result of all this respiration is heat, and for flowers the level of heat relative to the mass of the flower is very high. Respiration also brings about the eventual death of the flower. Thus the greater the level of respiration, the sooner the flower dies.

4.

How, then, to control the rate at which flowers die? By controlling respiration. How is respiration controlled? By controlling temperature. We know that respiration produces heat, but the reverse is also true. Thus by maintaining low temperatures, respiration is reduced and the cut flower will age more slowly.

5.

Another vital factor in keeping cut flowers is the quality of the water in which they are placed. Flowers find it difficult to “drink” water that is dirty or otherwise polluted. Even when water looks and smells clean, it almost certainly contains harmful substances that can endanger the flowers. To rid the water of these unwanted substances, household chlorine bleach (含氯漂白剂) can be used in small quantities. It is recommended that 15 drops of chlorine bleach(at 4% solution) be added to each litre of water. The water and solution should also be replaced each day.

When water is boiling, steam can be seen ______ from it.

根据短文内容, 从下框A~F选项中选出能概括每段主题的最佳选项，并在答题卡上将该选项涂黑。选项中有一项为多余项。

A. Control of respiration

B. Basic tips for preserving cut flowers

C. Role of respiration

D. Most important aspect of flower care

E. Need for clean water

F. Ways of stopping respiration

1.______________

While everybody enjoys fresh cut flowers around his house, few people know how to keep them for as long as possible. This may be done by keeping in mind a few simple facts. The key to keeping fresh cut flower for a week or more without preservatives ( which contain biocides (杀虫剂) that kill bacterial and fungus) is to keep the water fresh and the stems free of air pockets so they can continue to draw up water.

2._____________

  An important thing to remember about cut flowers is that they are sensitive to temperature. For example, studies have shown that cut carnations retain their freshness eight times longer when kept at 12℃ than when kept at 26℃. Keeping freshly harvested flowered at the right temperatures is probably the most important aspect of flower care.

3._____________

  The process by which flowers consume oxygen and produce carbon dioxide, called respiration (呼吸), supplies the energy the flower needs to give the flower its shape and color. The making of seeds also depends on this energy. While all living things respire, flowers have a high level of respiration. A result of all this respiration is heat, and for flowers the level of heat relative to the mass of the flower is very high. Respiration also brings about the eventual death of the flower. Thus the greater the level of respiration, the sooner the flower dies.

4.______________

  How, then, to control the speed at which flowers die? By controlling respiration. How is respiration controlled? By controlling temperature, we know that respiration produces heat, but the reverse ( 反面 ) is also true. Thus by keeping low temperatures, respiration is reduced and the cut flower will age more slowly.

5._____________

  Another vital factor in keeping cut flowers is the quality of the water in which they are placed. Flowers find it difficult to “drink” water that is dirty or otherwise polluted. Even when water looks and smells clean, it almost certainly contains harmful substances that can endanger the flowers. To rid the water of these unwanted substances, chlorine bleach ( 含氯漂白剂 ) can be used in small quantities. It is recommended that 15 drops of chlorine bleach be added to each liter of water. The water and solution （ 溶液 ）should also be replaced each day.

Energy is very important in modern life. People use energy to run machines, heat and cool their homes, cook, give light, and transport people and products from place to place. Most energy comes from fossil fuels—petroleum, coal, and natural gas. However, burning fuels causes pollution. Also, if we don’t find new kinds of energy, we will use up all the fossil fuels in the twenty-first century. Scientists are working hard to find other kinds of energy for the future. What might these sources of energy be?

                   Energy from the wind

   All over the world, people use the power of the wind. It turns windmills and moves sailboats. It is a clean source of energy, and there is lots of it. Unfortunately, if the wind does not blow, there is no wind energy.

Energy from water

   When water moves from a high place to a lower place, it makes energy. This energy is used to create electricity. In Brittany, France, for example, waterpower produces enough energy to light a town of 40,000people. Waterpower gives energy without pollution. However, people have to build dams to use this energy. Dams cost a lot of money, so water energy is expensive.

Energy from the earth

There is heat in rocks under the earth. Scientists use this heat to make geothermal energy. San Francisco gets half of the energy it needs from geothermal power. This kind of energy is cheap, but it is possible only in a few places in the world.

Energy from the sun

Solar panels on the roofs of houses can turn energy from the sun into electricity. These panels can create enough energy to heat an entire house. Solar power is clean and there is a lot of it in sunny places. But when the weather is bad, there is no sunlight for energy.

1.What does this passage mainly talk about?

   A．Advantage of the energy from nature.

   B．The future of the energy.

   C．Scientists have been working hard to research other kinds of energy.

   D．Energy is the most important power in the word.

2.From the first paragraph we know ______.

   A．energy can do everything for people

   B．all the energy causes pollution

   C．the new kinds of energy are badly needed

   D．scientists have found other kinds of energy for the future

3.What is the writer’s opinion about the energy?

   A．Try to use water energy more though it costs a lot.

   B．Each natural energy has its own advantages and disadvantages.

   C．Solar power is environmental.

   D．Wind power is the cheapest but we can’t get.

4.What can be inferred from the passage?

   A．In order to protect our environment, we should try other kinds of energy.

   B．All scientists in the world will unite to find energy.

   C．People in modern life use energy every day.

D．Energy changes people’s lives.