下面文章中有5处(第61～65题)需要添加小标题。请从以下选项(A、B、C、D、E和F)中选出符合各段意思的小标题。选项中有一项是多余选项。

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

小题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.

小题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.

小题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 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.

小题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.

小题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.

In considering how the American family is changing, the starting point is the traditional family. a form which has developed over time on the basis of a number of assumptions. It is assumed that the family is heterosexual (异性的) institution, with prescriptions about how a man and a woman ought to be joined together and live together. The proper family form is assumed to be the nuclear family, that is, a family composed of a married man and woman and their children. It is assumed that the husband is the head of the family, with ultimate authority over wife and children, and that in their clearly separated roles the husband is the income-earner and the wife is the homemaker and provider of child care. It is assumed that the family lives by itself in its own house or residence.

Observers of family life have suggested that numerous changes are taking place in this traditional American family form. Included are the following general observations about trends:

More men and women seem to be living together before getting married.

Women and men seem to be marrying at a later age.

Married couples are having fewer children.

Unmarried women appear to be having more children.

Wives, even mothers with small children, are increasingly likely to be employed outside the home.

Marriages are more likely to end with divorce.

Single-parent families are more prevalent.

Remarriage is likely to follow divorce rather than widowhood.

Remarriage rates are declining, especially for women.

Some trends, viewed in a long-range historical context, appear not to be trends at all. The age at which men and women normally marry is the same now as it was 100 years ago, though it has fluctuated (变动，波动); a short-range increase in the 1940s and 1950s due to widespread postponement of marriage in war time made it appear that a change had occurred. Other trends appear to be following established patterns rather than representing a sharp break with tradition. Divorce rates have been increasing and families have been having fewer children for well over a century. Single-parent families and stepfamilies were very common in the past, although the reason for them was different. Many marriages formerly are dissolved and followed by remarriage because of the death of a parent or partner. Today single parenthood and remarriage are more likely to be a response to divorce.

Some social scientists see in these changes the breakdown of the family, to the detriment of the society. We take the position that family institutions and systems, like all human systems, are open, take many forms, and are constantly changing.

According to the passage, the increase in divorce rates and single-parent families appear to ().

A. become the most obvious trend of all

B. follow established patterns

C. represent a sharp break with traditions

D. be the most harmful to society