试题库在线考试题库-历年真题模拟试题及答案-考博英语在线试题测试中心-希赛网

东北大学

Imagine eating everything delicious you want ― with none of the fat. That would be great, wouldn’t it?New “fake fat” products appeared on store shelves in the United States recently, but not everyone is happy about it. Makers of the products, which contain a compound called olestra, say food manufacturers can now eliminate fat from certain foods. Critics, however, say the new compound can rob the body of essential vitamins and nutrients and can also cause unpleasant side effects in some people. So it’s up to consumers to decide whether the new fat-free products taste good enough to keep eating.Chemists discovered olestra in the late 1960s, when they were searching for a fat that could be digested by infants more easily. Instead of finding the desired fat, the researchers created a fat than can’t be digested at all.Normally, special chemicals in the intestines “grab” molecules of regular fat and break them down so they can be used by the body. A molecule of regular fat is made up of three molecules of substances called fatty acids.The fatty acids are absorbed by the intestines and bring with them the essential vitamins A, D, E and K. When fat molecules are present in the intestines with any of those vitamins, the vitamins attach to the molecules and are carried into the bloodstream.Olestra, which is made from six to eight molecules of fatty acids, is too large for the intestines to absorb. It just slides through the intestines without being broken down. Manufacturers say it’s that ability to slide unchanged through the intestines that makes olestra so valuable as a fat substitute. It provides consumers with the taste of regular fat without any bad effects on the body. But critics say olestra can prevent vitamins A, D, E, and K from being absorbed. It can also prevent the absorption of carotenoids, compounds that may reduce the risk of cancer, heart disease, etc.Manufacturers are adding vitamins A, D, E, and K as well as carotenoids to their products now. Even so, some nutritionists are still concerned that people might eat unlimited amounts of food made with the fat substitute without worrying about how many calories they are consuming.1.We learn from the passage that olestra is a substance that （）.2.The result of the search for an easily digestible fat turned out to be （）.3.Olestra is different from ordinary fats in that （）.4.What is a possible negative effect of olestra according to some critics?5.Why are nutritionists concerned about adding vitamins to olestra?

The livelihood of each species in the vast and intricate assemblage of living things depends on the existence of other organisms. This interdependence is sometimes subtle, sometimes obvious. Perhaps the most straightforward dependence of one species on another occurs with parasites, organisms that live on or in other living things and derive nutrients directly from them. The parasitic way of life is widespread. A multitude of microorganisms (including viruses and bacteria) and an army of invertebrates — or creatures lacking a spinal column (including crustaceans, insects, and many different types of worms) — make their livings directly at the expense of other creatures. In the face of this onslaught, living things have evolved a variety of defense mechanisms for protecting their bodies from invasion by other organisms.Certain fungi and even some kinds of bacteria secrete substances known as antibiotics into their external environment. These substances are capable of killing or inhibiting the growth of various kinds of bacteria that also occupy the area, thereby eliminating or reducing the competition for nutrients. The same principle is used in defense against invaders in other groups of organisms. For example, when attacked by disease-causing fungi or bacteria, many kinds of plants produce chemicals that help to ward off their invaders.Members of the animal kingdom have developed a variety of defense mechanisms for dealing with parasites. Although these mechanisms vary considerably, all major groups of animals are capable of detecting and reacting to the presence of foreign cells. In fact, through the animal kingdom, from sponges to certain types of worms, shellfish, and all vertebrates (creatures possessing a spinal column), there is evidence that transplants of cells or fragments of tissues into an animal are accepted only if they come from genetically compatible or closely related individuals.The ability to distinguish between “sel” and “nonself”, while present in all animals, is most efficient among vertebrates, which have developed an immune system as their defense mechanism. The immune system recognizes and takes action against foreign invaders and transplanted tissues that are treated as foreign cells.1.What does the passage mainly discuss?2.The word “intricate” in Line One is closest in meaning to （）.3.According to the passage, some organisms produce antibiotics in order to （）.4.According to the passage, a transplant of tissue between genetically incompatible organisms will result in the transplanted tissue （）.5.According to the passage, the ability to distinguish between “self” and “nonself” enables vertebrates to （）.

As with any subject, people learn faster when concentration is high and we’re actively interested in learning. Being interested and relaxed helps too. In intensely verbal courses the teachers are most effective when they act as a facilitator. Their prime task is to grab attention, help make sure that the activities are interesting and provide background information, which helps students to actively participate in the lesson and plan and implement effective, complementary home study programs. The student is responsible for keeping himself or herself “Under Pressure” in the ways mentioned above. Of course this requires that students understand the types of pressure they should take upon themselves and when to back off. Imposed pressure is different in quality to self-imposed pressure, and it is the latter which is appropriate for adult learners, and children too, I suspect.In the typical actively verbal language class, understanding of the processes needed for effective language acquisition is necessarily inferred by the students. Communicating clearly with everyone in the class is difficult enough, so talking about why an activity is useful is quite likely to confuse and bemuse rather than enlighten students in a language course. For this reason transparent, open-ended activities with clear task goals form the foundation of any intensely verbal course. In other words, short demonstrations are followed by pair and group work doing the demonstrated activity and it is up to the students to make sure they involve themselves while the teacher is trying to target the activities so they are appropriate, allowing the students to discover for themselves ways in which the activity helps achieve their language target. Making activities appropriate is the key, meaning that students should be able to quickly realize that they can vary and extend what they are doing — that the example is a starting point, not a prescriptive pattern but a working start point which points them in a direction of exploration.1.What do you think the author has most probably talked about previously, according to the passage?2.When teachers are mentioned to act as a facilitator, they should be acting （）.3.Which of the following statements do you think that the writer will agree to?4.Which of the following statements is true according to the writer of this passage?5.What does the word “transparent” (Para. 2, line 4) mean?

Rocks which have solidified directly from molten materials are called igneous rocks. Igneous rocks are commonly referred to as primary rocks because they are the original source of material found in sedimentaries and metamorphics. Igneous rocks compose the greater part of the earth’s crust, but they are generally covered at the surface by a relatively thin layer of sedimentary or metamorphic rocks. Igneous rocks are distinguished by the following characteristics: (1) they contain no fossils; (2) they have no regular arrangement of layers and (3) they are nearly always made up of crystals.Sedimentary rocks are composed largely of minute fragments derived from the disintegration of existing rocks and in some instances from the remains of animals. As sediments are transported, individual fragments are assorted according to size. Distinct layers of such sediments as gravel, sand, and clay build up, as they are deposited by water and occasionally wind. These sediments vary in size with the material and the power of the eroding agent. Sedimentary materials are laid down in layers called strata.When sediments harden into sedimentary rocks, the names applied to them change to indicate the change in physical state. Thus, small stones and gravel cemented together are known as conglomerates; cemented sand becomes sandstone; and hardened clay becomes shale. In addition to these, other sedimentary rocks such as limestone frequently result from the deposition of dissolved material. The ingredient parts are normally precipitated by organic substances, such as shells of clams or hard skeletons of other marine life.Both igneous and sedimentary rocks may be changed by pressure, heat, solution, or cementing action. When individual grains from existing rocks tend to deform and interlock, they are called metamorphic rocks. For example, granite, an igneous rock, may be metamorphosed into a gneiss or a schist. Limestone, a sedimentary rock, when subjected to heat and pressure may become marble, a metamorphic rock. Shale under pressure becomes slate.1.The primary purpose of the passage is to （）.2.All of the following are sedimentary rocks EXCEPT （）.3.The passage would be most likely to appear in a （）.4.The relationship between igneous and sedimentary rocks may best be compared to the relationship between （）.5.The author’s tone in the passage can be best described as （）.

A transformation is occurring that should greatly（1）living standards in the developing world. Places that（2）recently were deaf and dumb are rapidly acquiring up-to-date telecommunications that will let them（3）both internal and foreign investment. It may take a decade for many developing countries to improve transportation, power supplies, and other（4）. Yet a single（5）fiber with a（6）of less than half a/an（7）can carry more information than a large cable made of copper wires. Many developing countries are planning to invest vast sum of money（8）their telecommunications networks to allow them to compete,（9）the transfer of information, with developed countries. How fast these nations should push ahead is a matter of debate.China is making one of the boldest leaps（10）carefully weighing costs and choosing（11）technologies. Over the next decade, it plans to pour some $100 billion into telecommunications equipment.（12）China’s backwardness is an advantage, because the expansion occurs（13）new technologies are becoming cheaper than copper wire systems. By the end of 1995, each of China’s（14）capitals except for Tibet will have digital（15）and other latest wireless transmission system. This means that major cities are getting the basic（16）to become major parts of the information superhighway, allowing people to（17）on to the most advanced services available.Telecommunications is also a key（18）Shanghai’s ambition of becoming a top financial center. To offer peak performance in providing the electronic data and paperless trading, Shanghai plans to be as electronically advanced （19）the City of New York.Some experts fear（20）that some developing countries are trying to do（21）too soon. Vietnam,（22）particular,（23）being extremely underdeveloped and lacking enough telephones of any type, is determined to contribute more money to the most expensive, newest technologies to keep（24）with anyone in Asia.Thailand is also turning to wireless, as a way to allow Thais to make better use of all the time they spend（25）in traffic. Mobile phones have become the（26）among businesspeople, who can remain in contact despite the traffic jams.For countries that have lagged behind for so long, the temptation to move ahead in one jump is hard to（27）. And （28）the mistakes they’ll make, they’ll persist —（29）one day they can cruise alongside Americans and Western Europeans（30）the information super highway.

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