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单选题Why may partial theories be completely wrong?

单选题Which of the following fiction belongs to the same group of Sister Carrie? A. The Luck of Roaring Camp. B. The Portrait of a Lady. C. The Gilded Age. D. Mc Teague.

单选题After meeting with Queen Elizabeth Ⅱ, ______came to his new official residency, Number 10 Downing Street, A. Tony Blair B. the King C. Gordon Brown D. president of Iraq

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单选题Formostpeoplewhohavesleepingtroubles,whichofthefollowingisthemostusualcause?

单选题 Questions 8 to 9 are based on the following news. At the end of the news item, you will be given 20 seconds to answer the questions. Now listen to the news.

单选题The growth of specialization in the 19th century might be more clearly seen in sciences such as ______.

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单选题This fishing village of 1,480 people is a bleak and lonely place. Set on the southwestern edge of Iceland, the volcanic landscape is whipped by the North Atlantic winds, which hush everything around them. A sculpture at the entrance to the village depicts a naked man facing a wall of seawater twice his height. There is no movie theater, and many residents never venture to the capital, a 50-min. drive away. But Sandgerdi might be the perfect place to raise girls who have mathematical talent. Government researchers two years ago tested almost every 15-year-old in Iceland for it and found that boys trailed far behind girls. That fact was unique among the 41 countries that participated in the standardized test for that age group designed by the Organization of Economic Cooperation and Development. But while Iceland's girls were alone in the world in their significant lead in math, their national advantage of 15 points was small compared with the one they had over boys in fishing villages like Sandgerdi, where it was closer to 30. The teachers of Sandgerdi's 254 students were only mildly surprised by the results. They say the gender gap is a story not of talent but motivation. Boys think of school as sufferings on the way to a future of finding riches at sea; for girls, it's their ticket out of town. Margret Ingporsdottir and Hanna Maria Heidarsdottir, both 15, students at Sandgerdi's gleaming school—which has a science laboratory, a computer room and a well-stocked library—have no doubt that they are headed for university. "I think I will be a pharmacist," says Heidarsdottir. The teens sat in principal Gudjon Kristjansson's office last week, waiting for a ride to the nearby town of Kevlavik, where they were competing in West Iceland's yearly math contest, one of many throughout Iceland in which girls excel. Meanwhile, by the harbor, Gisli Tor Hauksson, 14, already has big plans that don't require spending his afternoons toiling over geometry. "I'll be a fisherman," he says, just like most of his ancestors. His father recently returned home from 60 days at sea off the coast of Norway. "He came back with 1.1 million krona," about $18,000, says Hauksson. As for school, he says, "it destroys the brain." He intends to quit at 16, the earliest age at which he can do so legally. "A boy sees his older brother who has been at sea for only two years and has a better car and a bigger house than the headmaster," says Kristjansson. But the story of female achievement in Iceland doesn't necessarily have a happy ending. Educators have found that when girls leave their rural enclaves to attend universities in the nation's cities, their science advantage generally shrinks. While 61% of university students are women, they make up only one-third of Iceland's science students. By the time they enter the labor market, many are overtaken by men, who become doctors, engineers and computer technicians. Educators say they watch many bright girls suddenly flinch back in the face of real, head-to-head competition with boys. In a math class at a Reykjavík school, Asgeir Gurdmundsson, 17, says that 'although girls were consistently brighter than boys at school, "they just seem to leave the technical jobs to us." Says Solrun Gensdottir, the director of education at the Ministry of Education, Science and Culture: "We have to find a way to stop girls from dropping out of sciences." Teachers across the country have begun to experiment with ways to raise boys to the level of girls in elementary and secondary education. The high school in Kevlavik tried an experiment in 2002 and 2003, separating 16-to-20-year-olds by gender for two years. That time the boys slipped even further behind. "The boys said the girls were better anyway," says Kristjan Asmundsson, who taught the 25 boys. "They didn't even try./

单选题The theme of the book by Marie Winn is presumably

单选题The reviewer's attitude towards the book is

单选题What people brought the new religion Christianity to Britain first?[A] The Romans.[B] The Anglo-Saxons.[C] The Viking and Danish.[D] The Normans.

单选题What makes for a successful invasion? Often, the answer is to have better weapons than the enemy. And, as it is with people, so it is with plants—at least, that is the conclusion of a paper published in Biology Letters by Naomi Cappuccino, of Carleton University, and Thor Arnason, of the University of Ottawa, both in Canada. The phenomenon of alien species popping up unexpected parts of the world has grown over the past few decades as people and goods become more mobile and plant seeds and animal larvae have hitched along for the ride. Most such aliens blend into the ecosystem in which they arrive without too much fuss. (Indeed, many probably fail to establish themselves at all—but those failures, of course, are never noticed.) Occasionally, though, something goes bananas and starts trying to take the place over, and an invasive species is born. Dr. Cappuccino and Dr. Arnason asked themselves why. One hypothesis is that aliens leave their predators behind. Since the predators in their new homelands are not adapted to exploit them, they are able to reproduce unchecked. That is a nice idea, but it does not explain why only certain aliens become invasive. Dr. Cappuccino and Dr. Arnason suspected this might be because native predators are sometimes "pre-adapted" to the aliens' defences, but in other cases they are not. To test this, they had first to establish a reliable list of invaders. That is not as easy as it sounds. As they observe, "although there are many lists of invasive species published by governmental agencies, inclusion of a given species in the lists may not be entirely free of political motivation". Instead, they polled established researchers in the field of alien species, asking each to list ten invasive species and, for comparison, ten aliens that just rubbed along quietly with their neighbours. The result was a list of 21 species widely agreed to be invasive and, for comparison, 18 non-invasive aliens. Having established these lists, they went to the library to find out what was known about the plants' chemistry. Their aim was to find the most prominent chemical weapon in each plant, whether that weapon was directed against insects that might want to eat the plant, bacteria and fungi that might want to infect it, or other plants that might compete for space, water, nutrients and light. Botanists know a lot about which sorts of compounds have what roles, so classifying constituent chemicals in this way was not too hard. The researchers then compared the chemical arsenals of their aliens with those of native North American plants, to see if superior (or, at least, unusual) weaponry was the explanation for the invaders' success. Their hypothesis was that highly invasive species would have chemical weapons not found in native plants, and which pests, parasites and other plants would therefore not have evolved any resistance to. The more benign aliens, by contrast, were predicted to have arsenals also found in at least some native species. And so it proved. More than 40% of the invasive species had a chemical unknown to native plants, just over 10% of the non-invasive aliens had such a chemical. Moreover, when they looked at past studies on alien plants that had examined how much such plants suffer from the depredations of herbivorous insects, they found that the extent of the damage reported was significantly correlated with the number of native species with which that alien shared its principal chemical weapon. For alien plants, then, the real secret of success—also as in human warfare—is surprise. It is not that the chemicals concerned are more toxic in any general sense (indeed, successful invaders are often rare in their own native habitats). Rather, it is that the locals just don't see them coming.

单选题The longest river in Canada is ______.

单选题______ is the second largest country in the world.A. Canada.B.U.S.A.C. China.D. Russi

单选题The original New Zealand residents are ______. A. Eskimos B. Maoris C. Indians D. Inuits

单选题PaulRaysaidtheydiscoveredthataclearculturalchangewashappeninginmanyareasexcept______.A.people'slivesB.environmentalissuesC.consumptionpatternsD.mediaadvertisements

单选题The natives of the continent of America are the ______.

单选题The colonists first settled in ______ in Australia. A. South Australia B. Queensland C. Tasmania D. Victoria