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

海南大学

American astronomers high in the mountains of Puerto Rico have been trying to fathom the puzzle of the mysterious “pulsars” of deep space. These strange new signals were first picked up in 1967 on British radio telescopes. The signals originate from fifty to three hundred light years away, yet they always arrive at precise time intervals.Four pulsars have been located in a corner of our galaxy. And astronomers continue to look, or in this case, listen, since the pulsars are so far away that they cannot be detected by optical telescopes. The head of Cornell’s observatory in Puerto Rico says the energy used for these pulses is ten billion times greater than all the combined energy on earth.Several theories explaining the timed pulses have been offered. Most astronomers seem to believe these signals are a natural phenomenon. One idea is that a neutron star may be responsible. This is a star much like our sun, whose internal source of energy has burned out, causing it to collapse into mass of tremendous density.Another theory holds that some intelligent outer space civilization is producing the signals. There are strong arguments against that because pulsar energy seems wasted and the signals are spread over such a wide frequency range. Still another theory is that the signals come from stars that are invisible because civilizations that depend on them have built protective shells around them to conserve their energies.

There can be no doubt that sharks hear perfectly. Experience has shown that they react to the sound of blows under water, to the sound of a bell, or to the noises made by a diver at work. In general, their reaction is one of intense interest. I have often tried bits of advice like “If you see a shark approaching, beat the water with your hands,” or the famous warning given to beginning divers, “If you want to drive a shark away, cry out in the water.” In my experience, such advice is almost criminal. In most cases the consequence was an immediate attack.There seems to be no reason for the shark’s frenzy. This, I think, is what hits me most, giving me a feeling of complete helplessness. The mad rush of hordes of sharks toward the exact point where one of their own has devoured a bit of fish is terrifying to watch. The beasts seem unstoppable and fatal—and totally senseless.Sometimes the shark will flee from a naked and unarmed diver, and at other times he will throw himself against a steel diving cage and hit furiously at the vars. With any other animal—be it dog or crow—I know that my actions or reactions will have a direct influence on its behavior. But the shark moves through my world like a puppet whose strings are controlled by something other than the power moving mine; he seems to come from another planet. In fact, he does come from another time in that he has evolved little since his beginning. He perfectly adapts to his life, yet no one can ever predict what he will do.We do not know if sharks migrate from one region to another, but it has been established that the majority swim unceasingly, day and night. There are two reasons for this. Sharks do not have a “swimming bladder” (an organ that allows most fish to stabilize themselves at different depths). If sharks stop swimming they will sink. Also, most species have no mechanism for pumping water so that it will pass over their gills and bring oxygen into the bloodstream. They must depend on constant movement for this “breathing.”1. According to the writher, if we see a shark approaching, we should ______.2. Which of the following adjectives can best describe the shark’s rush towards the spot where some blood is ______.3. In paragraph 3, the writer describes the behavior of sharks in order to show ______.4. Which of the following statements about sharks is TRUE?5. The word “frenzy” most probably means ______.

In the primary school, a child is in a comparatively simple setting and most of the time forms a relationship with one familiar teacher. On entering secondary school, a new world opens up and frequently it is a much more difficult world. The pupil soon learns to be less free in the way he speaks to teachers and even to his fellow pupils. He begins to lose gradually the free and easy ways of the primary school, for he senses the need for a more cautious approach in the secondary school where there are older pupils. Secondary staff and pupils suffer from the pressures of academic work and seem to have less time to stop and talk. Teachers with specialist roles may see hundreds of children in a week, and a pupil may be able to form relationships with very few of the staff. He has to decide which adults are approachable; good schools will make clear to every young person from the first year what guidance and personal help is available—but whether the reality of life in the institution actually encourages requests for help is another matter.Adults often forget what a confusing picture school can offer to a child. He sees a great deal of movement, a great number of people—often rather frightening-looking people—and realizes that an increasing number of choices and decisions have to be made. As he progresses through the school the confusion may become less but the choices and decisions required will increase. The school will rightly expect the pupil to take the first steps to obtain the help he needs, for this is the pattern of adult life for which he has to be prepared, but all the time the opportunities for personal and group advice must be presented in a way which makes them easy to understand and within easy reach of pupils. (316 words)1. According to the passage one of the problems for pupils entering secondary schools is that ______.2. In secondary schools every pupil having problems should ______.3. It can be inferred from the passage that the author is mainly concerned about ______.4. Which of the following statements is TRUE?5. The most appropriate title for the passage would be ______.

It is doing something better than other people that makes us unique. Yet a surprising number of people still see individuality as a surface thing. They wear bright clothes, dye their hair strange colors and decorate their skin with tattoos to make some kind of social statement.The whole purpose of individuality is excellence. The people who comprehend the simple principle of being unique through performance make our entire political and economic system work. Those who invent, who improve, who know more about a subject than other people do, and who take something that doesn’t work and make it work—these people are the very soul of capitalism.Charles Kettering didn’t like the idea of cranking a car to make it start, so he invented the electric starter. Henry Ford figured out the assembly-line technique and made it possible to mass-produce automobiles. Lewis Waterman saw no need to go on dipping a pen into an inkwell, so he put the ink into the pen. George Westinghouse told the world how to stop a train, and Elisha Otis, inventor of the elevator, indirectly created the city skyline. These people understood that individualism means working at the top of one’s capacity.Fortunately, enough Americans have been inspired to do something with their uniqueness that we have developed in less than three centuries from a frontier outpost into not only a country of freedom but a country strong enough to protect that freedom. These people prized the notions of individuality and excellence above all things and thus kept the great machine functioning. The ones with the purple hair and the horrible jewelry are just along for the ride, trying to be “different” and not knowing how to go about it.The student who earns A’s on his report card has grasped the idea and has found the real meaning of individuality. So has the youngster who has designed his own spaceship, who paints pictures of the world around him, or who can name all the states and their capitals.1. According to the author unique individuals are persons who ______.2. People who regard individuality as a surface thing always do the following EXCEPT ______.3. Which is NOT true according to the passage?4. It can be inferred from the passage that ______.5. In the writer’s opinion who has understood the sense of individuality?

Plant vacuoles are frequently targeted as a storage site for novel products. We have used environment-sensitive fluorescent dyes and the expression of vacuolar marker proteins to characterize the vacuoles in different organs and cell types of sugarcane. The results demonstrated that the lumen of the vacuole in the parenchyma cells of the stem is acidic (<pH 5) and contains active proteases, characteristic of lytic vacuoles. In contrast to the stem parenchyma cells, the cells of sugarcane leaves contain diverse types of vacuoles. The pH of these vacuoles and their capacity to hydrolyze protease substrates varies according to cell type and developmental stage. Sugarcane suspension-cultures contain cells with vacuoles that resemble those of stem parenchyma cells and are thus a useful model system for investigating the properties of the vacuole.

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