投资者应当遵守(     )的原则，承担金融期货交易的履约责任，不得以不符合投资者适当性标准为由拒绝承担金融期货交易履约责任。

期货合约中的惟一变量是（　）。

    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.

    Is language, like food, a basic human need without which a child at a critical period of life can be starved and damaged? Judging from the drastic experiment of Frederick Ⅱ in the thirteenth century, it may be. Hoping to discover what language a child would speak if he heard no mother tongue, he told the nurses to keep silent. All the infants died before the first year. But clearly there was more than lack of language here. What was missing was good mothering. Without good mothering, in the
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/first year of life especially, the capacity to survive is seriously affected.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    Today no such severe lack exists as that ordered by Frederick. Nevertheless, some children are still backward in speaking. Most often the reason for this is that the mother is insensitive to the signals of the infant, whose brain is programmed to learn language rapidly.If these sensitive periods are neglected, the ideal time for acquiring skills passes and they might never be learned so easily again. A bird learns to sing and to fly rapidly at time, but the process is slow and hard once the critical stage has passed.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    Experts suggest that speech stages are reached in a fixed sequence and at a constant age, but there are cases where speech has started late in a child who eventually turns out to be of high IQ.At twelve weeks a baby smiles and utters vowel--like sounds; at twelve month she can speak simple words and understand simple commands; at eighteen months he has a vocabulary of three to fifty words. At three he knows about 1,000 words which he can put into sentences, and at four his language differs from that of his parents in style rather than grammar.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    Recent evidence suggests that an infant is born with the capacity to speak. What is special about man's brain, compared with that of the monkey, is the complex system which enables a child to connect the sight and feel of, say, a teddy bear with the sound pattern "teddy bear".And even more in-credible is the young brain's ability to pick out an order in language from the mixture of sound around him, to analyze, to combine and recombine the parts of a language in new ways.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    But speech has to be induced, and this depends on interaction between the mother and the child, where the mother recognizes the signals in the child's babbling, grasping and smiling, and responds to them. Insensitivity of the mother to these signals dulls the interaction because the child gets discouraged and sends out only the obvious signals. Sensitivity to the child's non-verbal signals is essential to the growth and development of language.

    So long as teachers fail to distinguish between teaching and learning, they will continue to undertake to do for children that which only children can do for themselves. Teaching children to readis not passing reading on to them. It is certainly not endless hours spent in activities about reading. Douglas insists that "reading cannot be taught directly and schools should stop trying to do the impossible."
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    Teaching and learning are two entirely different processes. They differ in kind and function. The function of teaching is to create the conditions and the climate that will make it possible for children to devise the most efficient system for teaching themselves to read. Teaching is also a public activity: It can be seen and observed.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    Learning to read involves all that each individual does to make sense of the world of printed language. Almost all of it is private, for learning is an occupation of the mind, and that process is not open to public scrutiny.
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/If teacher and learn roles are not interchangeable, what then can be done through teaching that will aid the child in the quest (探索) for knowledge? Smith has one principal rule for all teaching instructions. "Make learning to read easy, which means making reading a meaningful, enjoyable and frequent experience for children."
style=color: rgb(51, 51, 51); font-family: "Microsoft YaHei"; white-space: normal; background-color: rgb(250, 250, 250);/    When the roles of teacher and learner are seen for what they are, and when both teacher and learner fulfill them appropriately, then much of the pressure and feeling of failure for both is eliminated.Learning to read is made easier when teachers create an environment where children are given the opportunity to solve the problem of learning to read by reading.

中国期货业协会、期货交易所依法对期货市场客户开户实行( )。