单选题Whether you learn or not is entirely ________ you.

单选题These examples show that openness and the ability to change brings couples a giant step closer to the marital harmony they ______ .

单选题 Here's a question about chickens and eggs you may not have heard before: How is it that an egg can be so hard to break from the outside, yet so easy for a weak little chick to peck through from the inside? It's a tough question to crack. Eggshells are thought to change as the chick grows inside. As the creature develops, parts of the inner eggshell dissolve and the fuzzy little bird incorporates some of that calcium into its bones. But it remained unclear how this process influenced eggshell microstructure. Now, As Nicola Davis at The Guardian reports, a new study in Science Advances suggests that it's all about the structure of the egg and how it develops with the growing creature inside. To solve the mystery and study egg structures, researchers at McGill University used a new method that allowed them to cut extremely thin sections of shell. They then analyzed these thin sections using a microscope to study shell structure. The team examined the shell of fertilized (受精的)eggs and compared that to unfertilized eggs. As Laurel Hamers at ScienceNews reports, they discovered that the key to the eggs' toughness appeared to be the formation of microstructures, guided into place by proteins. They focused their analysis on one particular protein, which is found throughout the shell and is believed to be vital in the organization of mineral structure. As Davis explains, the special protein seems to act as a 'scaffold (脚手架)' that guides the structure and density of minerals in the shell, in particular calcium. In a developed egg, the minerals in the outer layer of the shell are densely packed and rich with such special protein. But inner egg layers have a different structure, which has less of such special protein and lower density of mineral packing. In non-incubated eggs, the nanostructure didn't change. But in the fertilized eggs, the structure of the inner egg appeared to shift over time. Calcium was transferred to the chicks and the inside of the shell grew weaker, making it easier for the chick to crack through. The inner shell also became bumpier (更崎岖不平的), which the researchers believe provides more surface area for chemical reactions that release calcium to the chicks. Knowing the structure of the egg could lead to new types of materials, says Lara Estroff, a Cornell engineer who was not involved in the study, Hamers reports. The researchers think it could even improve food safety for eggs. About 10 to 20 percent of chicken eggs crack in transport, which could lead to contamination. Understanding why some eggs are stronger than others could help breed chickens with tougher eggs.

单选题With summer coming on, the weather gets hot ______.

单选题 Child psychologists—and kindergarten teachers—have long known that when children first show up for school, some of them speak a lot more fluently than others. Psychologists also know that children's socioeconomic status tends to be closely connected with their language facility. The better off and more educated a child's parents are, the better vocabulary ability that child tends to have by school age—and vocabulary skill is a key predictor for success in school. Children from low-income families, who may often start school knowing significantly fewer words than their better-off peers, will struggle for years to make up that ground. Previous studies have shown that wealthier, educated parents talk to their young children more, using more complex vocabulary and sentences, than parents of lesser means. And these differences may help explain why richer kids start school with richer vocabularies. But what goes on before children can talk, during that phase—familiar to any parent—when communication takes the form of pointing, waving, grabbing and other kinds of baby sign language? Do well—off parents also gesture more to their kids? Indeed they do, say psychologists Susan Goldin-Meadow and Meredith Rowe of the University of Chicago. The researchers found that at 14 months of age, babies already showed a wide range of 'speaking' ability through gestures, and that those differences were closely linked with their socioeconomic background and how frequently their parents used gestures to communicate. High-income, better-educated parents gestured more frequently to their children to convey meaning and new concepts, and in turn, their kids gestured more to them. When researchers tested the same children at 54 months of age, they found that those early gesturers turned out to have better vocabulary ability than other students. At 14 months of age, researches say, pointing toward an object is the way most kids use gestures. If a parent responds to that gesture by identifying the object in words—by saying, 'That's a doll,' for example—children get a head start on growing their original vocabularies. 'That's a teachable moment, and mothers are teaching the kids the word for an object,' says Goldin-Meadow.

单选题Before high school teacher Kimberly Rugh got down to business at the start of a recent school week, she joked with her students about how she"d had to clean cake out of the comers of her house after her 2-year-old son"s birthday party. This friendly combination of chitchat took place not in front of a blackboard but in an Email message that Rugh sent to the 135 students she"s teaching at the Florida Virtual School, one of the nation"s leading online high schools. The school"s motto is "any time, any place, any path, any pace". Florida"s E-school attracts many students who need flexible scheduling, from young tennis stars and young musicians to brothers Tobias and Tyler Heeb, who take turns working on the computer while helping out with their family"s clam-farming business on Pine Island, off Florida"s southwest coast. Home-schoolers also are well represented. Most students live in Florida, but 55 hail from West Virginia, where a severe teacher shortage makes it hard for many students to take advanced classes. Seven kids from Texas and four from Shanghai round out the student body. The great majority of Florida Virtual Schoolers--80 percent are enrolled in regular Florida public or private high schools. Some are busy overachievers. Others are retaking classes they barely passed the first time. The school"s biggest challenge is making sure that students aren"t left to sink or swim on their own. After the school experienced a disappointing course completion rate of just 40 percent in its early years, Executive Director Julie Young made a priority out of what she calls "relationship-building", asking teachers to stay in frequent E-mail and phone contact with their students. That personal touch has helped: The completion rate is now 80 percent. Critics of online classes say that while they may have a limited place, they are a poor substitute for the face-to-face contact and socialization that take place in brick-and-mortar classrooms. Despite opportunities for online chats, some virtual students say they"d prefer to have more interaction with their peers. Students and parents are quick to acknowledge that virtual schooling isn"t for everyone. "If your child"s not focused and motivated, I can only imagine it would be a nightmare," says Patricia Haygood of Orlando, whose two daughters are thriving at the Florida school. For those who have what it takes, however, virtual learning fills an important niche. "I can work at my own pace, on my own time," says Hackney. "It"s the ultimate in student responsibility."

单选题 Honeybee populations declined by 13.6% over the winter, according to a survey of beekeepers across England. Losses were most severe in the north-east, where the survey recorded a loss rate of 17.1%. Experts worry that the declines will affect plant productivity. There are also concerns that the declines, along with drought conditions in some area, will mean less English honey this year. Martin Smith, president of the British Beekeepers Association, which carried out the survey, said: 'If this was measured against similar losses in livestock, it would be seen as disastrous and there would be great concern on the knock-on impact of food prices.' Beekeepers are puzzled by the decline because the cold winter and early spring should have favoured bees. They stay 'clustered' tightly in their hives when it is cold and dry, saving energy for spring foraging when the temperature rises about 12℃. However, there is good news that the rate of colony loss has slowed. Four years ago, one in three hives was wiped out. Beekeepers suspect that poor nutrition is a likely cause of weakness in adult bees that makes them succumb to diseases spread by a parasitic mite. 'The varroa mite is the number one reason why people lose bees, so the government needs to increase research to cure diseases caused by varroa,' said Smith. 'But a colony that has a good source of pollen and nectar will go into winter more strongly and better able to fend off disease.' The association is calling on everyone who has a garden, small, to plant bee-friendly plants this summer. 'It is really important that there are flowering nectar-rich plants around in August, September and October to provide the nutrition that's needed so the bees can top up their stores of honey in the hive to see them through winter,' said Smith. A campaign being launched next week to save all bees, spearheaded by Sam Roddick and Neal's Yard Remedies, pins the blame for the decline on pesticide. It will start a petition to hand to Downing Street in October to ban the use of a class of pesticides that has been implicated in bee deaths across the world. Roddick said, 'These neonicotinoid pesticides penetrate the plant and indiscriminately attack the nervous system of insects that feed off them, disorientating bees, impairing their foraging ability and weakening their immune system, causing bee Aids. On current evidence, Italy, Germany and Slovenia have banned some varieties. In the UK, it's up to the people to show the government that if there is any doubt that they are contributing to bee deaths, we need to ban them.' A spokesman for the government's National Bee Unit said: 'The UK has a robust system for assessing risks from pesticides and all evidence shows neonicotinoids do not pose an unacceptable risk when products are used correctly, but we will not hesitate to act if presented with any new evidence.'

单选题We must learn to see things in their right ______ and avoid making mistakes.

单选题The prizes will be______at the end of the school year.

单选题 Educators today are more and more often heard to say that computer literacy is absolutely necessary for college students. Many even argue that each incoming freshman should have permanent access to his or her own microcomputer. What advantages do computers offer the college students? Any student who has used a word processor will know one compelling reason to use a computer: to write papers. Although not all students feel comfortable composing on a word processor, most find revising and editing much easier on it. One can alter, insert, or delete just by pressing a few keys, thus eliminating the need to rewrite or re-type. Furthermore, since the revision process is less burdensome, students are more likely to revise as often as is necessary to end up with the best paper possible. For these reasons, many freshman English courses require the use of a word processor. Computers are also useful in the context of language courses, where they are used to drill students in basic skills. Software programs reinforce ESL (English as a Second Language) instruction, as well as instruction in French, German, Spanish, and other languages. By using these programs on a regular basis, students can improve their proficiency in a language while proceeding at their own pace. Science students take advantage of computers in many ways. Using computer graphic capabilities, for example, botany students can represent and analyze different plant growth patterns. Medical students can learn to interpret computerized images of internal body structures. Physics students can complete complex calculations far more quickly than they could without the use of computer. Similarly, business and accounting students find that computer spreadsheet programs are all but indispensable to many aspects of their work, while students pursuing careers in graphic arts, marketing, and public relations find that knowledge of computer graphic is important. Education majors learn to develop grading systems using computers, while social science students use computers for analyzing and graphically displacing their research results. It is no wonder, then, that educators support the purchase and use of microcomputers by students. A versatile tool, the computer can help students learn. And that is, after all, the reason for going to college.

单选题It is still not clear what ______ a series of argument between them.

单选题 For the sake of animal protection, environmentalists deplored the construction program of a nuclear power station.

单选题Consumers deprived of the information and advice they needed were quite simply ______ very cheat in the marketplace.

单选题The managing director took the ______ for the accident, although it was not really his fault. A. guilt B. blame C. charge D. accusation

单选题The technological advances made it possible for the middle classes to enjoy what had once been ______ only to the very rich.

单选题This is an alarming realization as natural resources and the environment are being degraded and ______ at a record pace.

单选题I got caught in the rain and my suit ______.

单选题Economic theory would predict that a fall in the price of a commodity would lead to an increase in ______. A. assumption B. resumption C. consumption D. presumption

单选题Respect for the law is the foundation of civilized living. ______ breaks it will be punished.

单选题A: I gambled away all the money I won from the lottery last week.B: ______