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.

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.

根据短文内容，从短文后的选项中选出能填入空白出的最佳选项。选项中有两项为多余选项。

   What do you, the trees, and a bird have in common?      71     . All living things must have water to survive, whether they get it from a water fountain, a rain cloud, or a little bottle attached to the side of a bird cage.

    72      Water makes up more than half of your body weight and a person can’t survive for more than a few days without it. Why? Your body has lots of important jobs and it needs water to do many of them. For instance（例如）, your blood, which contains a lot of water, carries oxygen to all the cells (细胞) of your body. Without oxygen, those tiny cells would die and your body would stop working.

   Water is a fluid (流体) that is part of your immune system (免疫系统) , which helps you fight off illness.      73      Water is needed for digestive juices (消化液) , urine（尿）, and makes up most of sweat.

   In addition to being an important part of the fluids in your body, each cell depends on water to function normally.

     74     Any fluid you drink will contain water, but water and milk are the best choices. Lots of foods contain water, too.      75     You could probably tell that if you’ve ever bitten into a peach or pear and felt the juices dripping down your chin (下巴) ! Vegetables, too, contain a lot of water------think of biting into a fat tomato from the garden.

A. You need water to digest your food and get rid of water, too.

B. You all need water.

C. Without water, your body would stop working properly.

D. How much is enough?

E. Your body doesn’t get water only from drinking water.

F. When you drink is also important.

G. Fruit contains quite a bit of water.