Keeping Cut Flowers
1 While everybody enjoys fresh cut flowers around their 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.
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（二氧化碳）, called respiration（呼吸）, generates 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 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 liter of water. The water and solution should also be replaced each day.
23 Paragraph 2 .
24 Paragraph 3 .
25 Paragraph 4 .
26 Paragraph 5 .
A Control of Respiration
B Beauty of Fresh Cut Flowers
C Role of Respiration
D Most Important Aspect of Flower Care
E Need for Clean Water
F Ways of Stopping Respiration
27 A few simple facts will help you keep cut flowers .
28 Respiration plays a key role .
29 The aging of cut flowers can be slowed down .
30 Another important way to prolong the life of cut flowers is .
A by keeping its original shape and color
B in the life of cut flowers
C to produce carbon dioxide
D for as long as possible
E by controlling temperature
F to replace the water and solution every day
答案：
23. D 24. C 25. A 26. E 27. D 28. B 29. E 30. F
解析：
23 D 第二段中最后一句为段落中心句，所以不难选出答案为D,
24 C 第三段主要讲的是呼吸对切花寿命的影响，本段中一直穿插respiration这个关键词，并且最后一句为主题句。Thus the greater the level of respiration, the sooner the flower dies.点出了呼吸对切花的重要作用。所以选C.
25 A 第四段开头就提出问题：怎样控制切花的死亡率，后边紧接着讲通过控制温度来调节呼吸进而起到控制死亡率的目的。所以应该选A.
26 E 第五段开头一句是中心句，这一段主要讲的是水的条件对切花的作用，所以应该选E.
27 D 文章主要讲的是怎样保持切花的寿命及新鲜度。所以该题应该选择D
28 B 文章的第三段就是讲呼吸对切花寿命的影响，所以应该选择B
29 E 第三段第一句讲到通过调节温度事先控制呼吸，进而影响到切花的寿命，所以应该选温度。
30 F 见文章最后一段的第一句话，提到了保护切花寿命的另一种方法就是保证给予无污染的水。所以应该选择F.
