单选题In previous times, when fresh meat was inadequate , pigeons were kept by many households as a source of food.

单选题Because of Oden's uniqueness, he is always performing in the spotlight and subject to public scrutiny. A. ridicule B. censorship C. examination D. criticism

单选题The other, more publicly acceptable form of geo-engineering would focus on removing carbon from the atmosphere and storing it underground. Known as carbon capture and storage (CCS), this idea is behind today's experimental clean-power plants, which are attracting lots of research and funding. But clean, coal plants will only reduce future emissions, which does not address the root of the problem. Among all the uncertainties that still surround climate change, one thing has become clear: the scary durability of carbon, which will hang in the air for a thousand years, continuing to warm the planet no matter how drastically future emissions are cut. So there is a growing urgency behind the geo-engineer's dream: to change the climate by artificial means, either sucking the existing carbon out of the air or cooling the air with solar reflectors. Why is carbon so scary according to the passage?A. It will contihue to warm the globe for many years.B. It cannot be easily captured and stored.C. Its emission will increase in the coming years.D. It cannot be reflected back into the spac

单选题I am not certain whether he will come.

单选题Certainly we need law or else society will deteriorate to provide survival, but it doesn't create Ucooperation/U.

单选题They have the capability to destroy the enemy in a few days.

单选题"You want me to send in three men to dig the box up, without making a sound, and Uget rid of/U it properly?"

单选题 Trees 1. Trees are plants that survive year after year and have a single main stem composed entirely of wood. Some kinds grow to only ten feet. Others attain heights of more than 350 feet. These giants also have stems that are as much as 100 feet in circumference (圆周). 2. Over 25,000 different species of tree grow around the wood, except near the North and South Poles. They all belong to one of two possible groups. They are either coniferous (松类的) or deciduous (落叶的). Coniferous trees are evergreens (常绿的), such as pine or fir, which bear needlelike foliage (叶子) all year long. Many deciduous trees have broad leaves, which they usually shed each year at the beginning of the cold season. 3. Trees provide people with a host of oils, drugs, glues, candy, cloths, fuels, and well over 10,000 wooden products. Some have unique qualities that make their wood valuable for special purposes. One particular type of tree, for example, is used to make fishing rods because it is not strong but unusually flexible. Queensland walnut is used by the electrical industry in Australia, because it is almost as good an electrical insulator as rubber. One of the world most unusual trees is the teak (柚木). It is one of the heaviest of all woods, and it has the largest leaves of any tree. These enormous leaves are two feet square and their surface is so tough and coarse that cabinetmakers in India use them as sandpaper. Teakwood itself is so heavy that when a teak tree is first cut down it will not float in water. It takes three years for the ten or fifteen-ton trunk to dry out enough so it will not sink. 4. Of all the world's billions of living trees, the tallest is a giant redwood in California. It towers 368 feet. This redwood tree is anchored and nourished by a massive root system. It extends over three full acres.

单选题Early United States Reinterpreted by Bernard Bailyn Bernard Bailyn has recently reinterpreted the early history of the United States by applying new social research findings on the experiences of European migrants. In his reinterpretation, migration becomes the organizing principle for rewriting the history of preindustrial North America. His approach rests on four separate propositions. The first of these asserts that residents of early modern England moved regularly about their countryside; migrating to the New World was simply a natural spillover. Although at first the colonies held little positive attraction for the English—they would rather have stayed home—by the eighteenth century people increasingly migrated to America because they regarded it as the land of opportunity. Secondly, Bailyn holds that, contrary to the notion that used to flourish in America history textbooks, there was never a typical New World community. For example, the economic and demographic character of early New England towns varied considerably. Bailyn"s third proposition suggests two general patterns prevailing among the many thousands of migrants: one group came as indentured servants, another came to acquire land. Surprisingly, Bailyn suggests that those who recruited indentured servants were the driving forces of transatlantic migration. These colonial entrepreneurs helped determine the social character of people who came to preindustrial North America. At first, thousands of unskilled laborers were recruited; by the 1730"s, however, American employers demanded skilled artisans. Finally, Bailyn argues that the colonies were a half-civilized hinterland of the European culture system. He is undoubtedly correct to insist that the colonies were part of an Anglo-American empire. But to divide the empire into English core and colonial periphery, as Bailyn does, devalues the achievements of colonial culture. It is true, as Bailyn claims, that high culture in the colonies never matched that in England. But what of seventeenth-century New England, where the settlers created effective laws, built a distinguished university, and published books? Bailyn might respond that New England was exceptional. However, the ideas and institutions developed by New England Puritans had powerful effects on North American culture. Although Bailyn goes on to apply his approach to some thousands of indentured servants who migrated just prior to the revolution, he fails to link their experience with the political development of the United States. Evidence presented in his work suggests how we might make such a connection. These indentured servants were treated as slaves for the period during which they had sold their time to American employers. It is not surprising that as soon as they served their time they passed up good wages in the cities and headed west to ensure their personal independence by acquiring land. Thus, it is in the west that a peculiarly American political culture began, among colonists who were suspicious of authority and intensely anti-aristocratic.

单选题The contract between the two companies will {{U}}expire{{/U}} soon. A. shorten B. end C. start D. resume

单选题The staff of the company are always {{U}}courteous{{/U}} and helpful.

单选题Writing is a skill that requires {{U}}consistent {{/U}}practice.

单选题 Obtaining Drinking Water from Air Humidity Not a plant to be seen, the desert ground is too dry. But the air contains water, and research scientists have found a {{U}} {{U}} 1 {{/U}} {{/U}}of obtaining drinking water from air humidity. The system is based completely on renewable energy and is therefore autonomous. Cracks permeate the dried-out desert ground and the landscape bears testimony to the lack of water. But even here, where there are no lakes, rivers or groundwater, considerable quantities of water are stored in the air. In the Negev desert in Israel, for example, annual average relative air humidity is 64 percent-in every cubic meter of air there are 11.5 milliliters of water. German research scientists have found a way of converting this air humidity autonomously into drinkable water. "The process we have developed is based exclusively on renewable energy sources {{U}} {{U}} 2 {{/U}} {{/U}}thermal solar collectors and photovoltaic ceils, {{U}} {{U}} 3 {{/U}} {{/U}}makes this method completely energy-autonomous. It will {{U}} {{U}} 4 {{/U}} {{/U}}function in regions where there is no electrical infrastructure." says Siegfried Egner, head of the research team. The principle of the {{U}} {{U}} 5 {{/U}} {{/U}}is as follows: hygroscopic brine-saline solution which absorbs moistureruns down a tower-shaped unit and absorbs water from the air. It is then sucked {{U}} {{U}} 6 {{/U}} {{/U}}a tank a few meters off the ground in which a vacuum prevails. Energy from solar collectors {{U}} {{U}} 7 {{/U}} {{/U}}up the brine, which his diluted by the water it has {{U}} {{U}} 8 {{/U}} {{/U}}. Because of the vacuum, the boiling point of the liquid is lower than it would be under {{U}} {{U}} 9 {{/U}} {{/U}}atmospheric pressure. This effect is known from the mountains: as the atmospheric pressure there is lower than in the valley, water boils at temperatures distinctly below 100℃. The evaporated, non-saline water is condensed and runs down through a completely filled tube in a controlled manner. The gravity of this water column {{U}} {{U}} 10 {{/U}} {{/U}}produces the vacuum and so a vacuum pump is not needed. The reconcentrated brine {{U}} {{U}} 11 {{/U}} {{/U}}down the tower surface again to absorb moisture from the air. "The concept is suitable for various water {{U}} {{U}} 12 {{/U}} {{/U}}. Single-person units and plants supplying water to entire hotels are conceivable, " says Egner. Prototypes have been built for {{U}} {{U}} 13 {{/U}} {{/U}}system components-air moisture absorption and vacuum evaporation-and the research scientists have already {{U}} {{U}} 14 {{/U}} {{/U}}their interplay on a laboratory scale. In a further {{U}} {{U}} 15 {{/U}} {{/U}}the researchers intend to develop a demonstration facility.

单选题We're happy to collaborate with you in the project. A. compete B. cooperate C. coordinate D. contend

单选题From my standpoint, this thing is just ridiculous A. field B. point of view C. knowledge D. information

单选题What is the writer’s attitude to robots in the future?

单选题His claims seem Ucredible/U to many people.

单选题The girl is {{U}}gazing{{/U}} at herself in the mirror.

单选题阅读下面的短文，文中有15处空白，每处空白给出4个选项，请根据短文的内容从4个选项中选择1个最佳答案。 Energy equals mass times the speed of light squared. This is the famous equation of Albert Einstein. It{{U}} (51) {{/U}}to the category of the theory of relativity, and it equates energy with mass. All things are made up of atoms. When{{U}} (52) {{/U}}of an atom travels at almost the speed of light{{U}} (53) {{/U}}we put more energy into it to increase the speed, it begins to in crease in mass. The energy that makes it travel fast cannot make it travel{{U}} (54) {{/U}}the speed of light—nothing{{U}} (55) {{/U}}light can travel that fast- so the energy goes into the thing{{U}} (56) {{/U}}and increases its mass. Energy{{U}} (57) {{/U}}into mass. Why is the theory called the theory of relativity? A thing that is relative depends upon{{U}} (58) {{/U}}else to identify it or to define it. In relativity theory we identify or define mass, time, and length{{U}} (59) {{/U}}to the speed of light. When something is at rest, it looks{{U}} (60) {{/U}}in length. However, when it travels at almost the speed of light, it becomes{{U}} (61) {{/U}}. Time also changes. However, the change in time is{{U}} (62) {{/U}}to the change in length. The length of a thing becomes short{{U}} (63) {{/U}}time becomes long. If you want to{{U}} (64) {{/U}}young, relative to a friend, take a trip in a spaceship that travels at{{U}} (65) {{/U}}the speed of light. And, although time and heartbeat seem ordinary to you in the spaceship, when you return, look at your friend; Relative to you, he or she is old.

单选题Birdsong A male zebra finch chirps away to himself. Suddenly he notices a female bird nearby. He realizes he has an audience and immediately changes his song. Can the female tell the difference in his performance? According to a new study, the female zebra finch knows. And she prefers the special trills he creates when he sings to her. A male zebra finch changes his song when singing to a female in ways that people can barely detect. But the female finch can tell the difference. Scientists had noticed slight variations in the songs of male zebra finches based on whether they were singing alone or whether there was a female (and potential mate) nearby. With an audience, the males sped up the pace of their songs and controlled the notes they used. For this study, researchers Sarah C. Woolley and Allison Doupe at the University of California, San Francisco decided to focus attention on the listening females, which have not been well studied in the past. In the study, Woolley and Doupe set up, a long cage with a sound speaker at each end. One broadcast the sound of a male zebra finch singing to himself, like someone singing in the shower. The other speaker broadcast a male performing for a female audience, as if he was giving a concert. Female birds were placed between the two speakers. Some of the birds had mates, others didn't. The females shifted around a bit, and then most of them hopped over to sit beside just one speaker. All the birds that made a clear choice liked songs meant for a female audience, even if they'd never met the male. Mated females also had a chance to listen to two different performance songs, one from an unknown male, and one from their mate. They spent more time listening to the concert version of their mates' songs. This suggests that after a while, females learn to recognize and prefer the songs of their mates. Scientists then studied the brains of the females. They found certain areas of the brain perked up when the birds listened to the concert songs. These brain areas may be involved in recognizing and evaluating the songs, and storing the memories of them. This research deals with what's called directed communication, when the communicator, or sender, focuses the message for a specific audience. One example is the way moms speak to their babies. Mothers around the world use the same sort of high-pitched sing-song chatter, and the babies respond best to those sounds. Songbirds are one of the only other species known to learn their communication, in this case their songs.