单选题Conventional wisdom has long held that mammals stayed millions of years on earth. As long as dinosaurs roamed the lands, our distant ancestors never got to be much more than chicken-hearted creatures that sneaked out at night to grab bits of plants when the terrible lizards were asleep. Only when they were wiped out did mammals begin to earn a little evolutionary respect. But that picture changed dramatically with the announcement in Nature of two impressive fossils. One, of a brand-new species named R. giganticus , broke apart the notion that most dinosaur-age mammals were never larger than squirrels. The animal had the dimensions of a midsize dog-by far the biggest dinosaur-age mammal ever found. And the second, a new specimen of a previously discovered species called R. robustus , refuted the notion that it was always the mammals that got eaten. Inside the skeleton where the animal"s stomach would have been are the fossilized remains of a baby dinosaur. "This discovery was the chance of a lifetime," says Jin Meng, scientist and coauthor of the paper. Indeed, Meng didn"t expect to find things like this at all. The smaller skeleton was discovered about two years ago by villagers in China"s Liaoning province, site of some of the richest fossil beds in the world. They brought it to the attention of scientists, who took it to an institute for examination. "We didn"t see the stomach contents at first," says Meng. After they did, however, it didn"t take them long to realize they had struck scientific gold. On closer examination, the scientists determined that the remains were those of a juvenile dinosaur. Some of the arm and leg bones were still attached to each other, suggesting that R. robustus didn"t chew its food thoroughly but wolfed it down in large chunks. Taken together, the finds overturn the already eroded idea that early mammals were tiny and timid. Now paleontologists can stop cooking up theories to explain why mammals were so little—that they had to be small to avoid being found, for example, or they couldn"t grow larger because dinosaurs already occupied those ecological spaces. But it"s now clear that mammals did fill some of the spaces reserved for larger animals. "It"s quite possible," says paleontologist Anne Weil, "that they competed with dinosaurs for the same prey." And because they ate dinosaurs, they may even have had an influence on dinosaur evolution. What sort of influence? "We don"t know," she says. "That"s how it is with the best finds. They leave you with more questions than answers."

单选题She had just finished her homework ______ her mother asked her to practice playing the piano yesterday. A. while B. when C. after D. since

单选题 Questions 14～17 are based on a dialogue about intermarriage, You now have 20 seconds to rend Questions 14～17.

单选题This article is about

单选题Pragmatism is a philosophical movement that has had a major impact on American culture from the late 19th century to the present. Pragmatism calls 1 ideas and theories to be tested in practice, by 2 whether acting upon the idea or theory produces desirable or undesirable results. The ideas of the pragmatists were considered 3 when they first appeared. To some critics, pragmatism"s 4 to affirm any absolute standards carried negative implications for society. 5 , pragmatists do not believe that a single absolute idea of goodness or justice exists, but 6 that these concepts are changeable and depend on the 7 in which they are being discussed. The 8 of these absolutes, critics feared, could result in a (n) 9 in moral standards. The pragmatists" denial of absolutes, 10 , challenged the foundations of religion, government, and schools of thought. 11 , pragmatism influenced developments in psychology, sociology, and many other schools and movements. 12 political groups have also drawn 13 the assumptions of pragmatism, from the progressive movements of the early 20th century to later experiments in social reform. Pragmatism is best 14 in its historical and cultural context. It arose during the late 19th century, a period of rapid scientific advancement 15 by the theories of British biologist Charles Darwin, whose theories 16 to many thinkers that humanity and society are in a 17 state of progress. During this same period, a decline in 18 religious beliefs and values accompanied the industrialization and material progress of the time. In 19 , it became necessary to rethink 20 ideas about values, religion, science, community, and individuality.

单选题 It's plain common sense—the more happiness you feel, the less unhappiness you experience. It's plain common sense, but it's not true. Recent research reveals that happiness and unhappiness are not really two sides of the same emotion. They are two distinct feelings that, coexisting, rise and fall independently. People might think that the higher a person's level of unhappiness, the lower their level of happiness and vice versa. But when researchers measure people's average levels of happiness and unhappiness, they often find little relationship between the two. The recognition that feelings of happiness and unhappiness can coexist much like love and hate in a close relationship may offer valuable clues on how to lead a happier life. It suggests, for example, that changing or avoiding things that make you miserable may well make you less miserable, but probably won't make you any happier. That advice is backed up by an extraordinary series of studies which indicate that a genetic predisposition for unhappiness may run in certain families. On the other hand, researchers have found happiness doesn't appear to be anyone's heritage. The capacity for joy is a talent you develop largely for yourself. Psychologists have settled on a working definition of the feeling—happiness is a sense of subjective well-being. They have also begun to find out who's happy, who isn't and why. {{U}}To date, {{/U}}the research hasn't found a simple formula for a happy life, but it has discovered some of the actions and attitudes that seem to bring people closer to that most desired of feelings. Why is unhappiness less influenced by environment? When we are happy, we are more responsive to people and keep up connections better than when we are feeling sad. This doesn't mean, however, that some people are born to be sad and that's that. Genes may predispose one to unhappiness, but disposition can be influenced by personal choice. You can increase your happiness through your own actions.