The predictability of our mortality rates is something that has long puzzled social scientists. After all, there is no natural reason why 2,500 people should accidentally shoot themselves each year or why 7,000 should drown or 55,000 die in their cars. No one establishes a quota for each type of death. It just happens that they follow a consistent pattern year after year.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    A few years ago a Canadian psychologist named Gerald Wilde became interested in this phenomenon. He noticed that mortality rates for violent and accidental deaths throughout the western world have remained oddly static throughout the whole of the century, despite all the technological advances and increases in safety standards that have happened in that time. Wilde developed an intriguing theory called "risk homeostasis". According to this theory, people instinctively live with a certain level of risk. When something is made safer, people will get around the measure in some way to reassert the original level of danger. If, for instance, they are required to wear seat belts, they will feel safer and thus will drive a little faster and a little more recklessly, thereby statistically canceling out the benefits that the seat belt confers. Other studies have shown that where an intersection is made safer, the accident rate invariably falls there but rises to a compensating level elsewhere along the same stretch of road. It appears,then, that we have an innate need for danger.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    In all events, it is becoming clearer and clearer to scientists that the factors influencing our lifespan are far more subtle and complex than "had been previously thought. It now appears that if you wish to live a long life, it isn't simply a matter of adhering to certain precautions eating the foods, not smoking, driving with care. You must also have the attitude. Scientists at the Duke University Medical Center made a 15-year study of 500 persons personalities and found, somewhat to their surprise, that people with a suspicious or mistrustful nature die prematurely far more often than people with a sunny disposition. Looking on the b side, it seems, can add years to your lifespan.

    There are people who are especially attracted to the notion of "climbing the ladder" so as to increase their status, financial position, and sense of self-worth. In part, as a result of the work ethic, these people are internally "driven" to work. Not infrequently, foreign visitors have observed that Americans spend an inordinate(过度的)amount of time working and, as a consequence, Americans have little time for leisure or personal relationships. In American English a new word"workaholic" has been created to describe an individual who is as addicted to work as an alcoholic (酒鬼)is to liquor.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    There are conflicting points of view about workaholics. Those concerned with problems of mental stress believe workaholics abuse themselves physically and mentally. Others hold that workaholics are valuable members of society because they are extremely productive. The Americans culture values achievement, efficiency, and production--a workaholic supports these values.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    Despite the presence of workaholics,there is a growing realization in the United States that excessive work demands can be physically and mentally harmful. Many people have been rebelling against the work ethic, claiming that when a job is so important, personal relationships suffer and relaxation becomes secondary. Consequently there has been a shift in values, with more emphasis being given to personal relationships and non-work activities.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    Increased leisure time in the United States has not changed the idea that work and play are distinct activities."There is a belief that it is desirable" to work hard and play hard,and undesirable to combine the two. In many offices, stores and factories socializing among employees is discouraged. An employee under pressure at work often cannot afford to respond to social calls and visits. However, the amount of personal contact on the job depends on the nature of the work.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    People are ambivalent (矛盾的)toward work; it is, at the same time, glorified and belittled. In the words of former President Richard Nixon: "The 'work ethic' holds that labor is good in itself; that a man or woman becomes a better person by virtue of the act of working. America' s competitive spirit, the 'work ethic' of this people, is alive and well ..." Another viewpoint is expressed in an Anacin commercial:"I like my job and am good at it, but it sure grinds me down( 折磨 )sometimes, and the last thing I need to take home is a headache."

    Protests at the use of animals in research have taken a new and fearful character in Britain with attempted murder of two British scientists by the terrorist technique of the pre-planted car bomb.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    The research community will ly be alarmed at these developments, which have two aims:to draw public attention and to fen people working in research with animals. The scientists insist that everything should be done to identify those responsible for the crimes and to put them on trial. The Defense Research Society has taken the practical step ofoffering a reward of $10,000 for information leading to those responsible, but past experience is not encouraging. People are unlikely to be tempted by such offers. The professional police will similarly be confronted by the usual problem of finding a needle in a haystack.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    That is why the intellectual community in Britain and elsewhere must act more actively in its own defense. There are several steps that can be taken, of which the chief one is to demand of all the organizations that exist with the declared aims of.safeguarding the interests of animals that they should declare clearly where they stand on violence towards people. And it will not be enough for the chairman and chairwoman of these organizations to make placatory statements on behalf of all their members. These people should also undertake that it will be a test of continuing membership in their organizations that members and would-be members should declare that they will take no part in acts of violence against human beings. Even such undertakings would be fully effective: people, after all, can lie. But at least they would distinguish the organizations entitled to a continuing voice in the dialogue with the research community about the s of animals in research from the organizations that deserve no say.

    Protests at the use of animals in research have taken a new and fearful character in Britain with attempted murder of two British scientists by the terrorist technique of the pre-planted car bomb.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    The research community will ly be alarmed at these developments, which have two aims:to draw public attention and to fen people working in research with animals. The scientists insist that everything should be done to identify those responsible for the crimes and to put them on trial. The Defense Research Society has taken the practical step ofoffering a reward of $10,000 for information leading to those responsible, but past experience is not encouraging. People are unlikely to be tempted by such offers. The professional police will similarly be confronted by the usual problem of finding a needle in a haystack.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    That is why the intellectual community in Britain and elsewhere must act more actively in its own defense. There are several steps that can be taken, of which the chief one is to demand of all the organizations that exist with the declared aims of.safeguarding the interests of animals that they should declare clearly where they stand on violence towards people. And it will not be enough for the chairman and chairwoman of these organizations to make placatory statements on behalf of all their members. These people should also undertake that it will be a test of continuing membership in their organizations that members and would-be members should declare that they will take no part in acts of violence against human beings. Even such undertakings would be fully effective: people, after all, can lie. But at least they would distinguish the organizations entitled to a continuing voice in the dialogue with the research community about the s of animals in research from the organizations that deserve no say.

期货合约中的惟一变量是（　）。