华师大《综合英语（3）》在线作业

奥鹏华中师范大学平时在线作业

华师《综合英语（3）》在线作业-0004

About 200 million years ago, as the Triassic Period came to a close, many species of animals disappeared from the face of the Earth. Scientists previously believed that the series of extinctions happened over a period of 15 to 20 million years. Recent discoveries in Nova Scotia suggest, however, that the extinctions may have happened over a much shorter period of time, perhaps less than 850,000 years.Evidence for a rapid extinction of species at the enc of the Triassic Period is found in the McCoy Brook Formation along the Bay ofFundy in Nova Scotia. Fossils found in this formation indicate a rapid disappearance of species rather than a slow and gradual change over time. One explanation for a relatively sudden extinction at the end of the Triassic may be that a large meteorite struck the earth at the time and is responsible for a 70-kilometer hole nearby. If geologists and other researches can find evidence, such as shocked quartz in the rock formations, that a meteorite did strike the earth, it would give more credence to the theory of rapid Triassic extinctions. It is possible, however, that even if a rapid extinction happened in and around Nova Sctia, it didnt necessarily occur in the rest of the world.
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Franklin D. Roosevelt, the 32nd president of the United States, was from a wealthy, well-known family. As a child, he attended private school, had private tutors, and traveled with his parents to Europe. He attended Harvard University, and afterward studied law. At age 39 Roosevelt suddenly developed polio, a disease that left him without the full use of his legs for the rest of his life. Even through the worst of his illness, however, he continued his life in politics. In 1924 he appeared at the Democratic National Convention to nominate Al Smith for president, and eight years after that he himself was nominated for the same office. Roosevelt was elected to the presidency during the Great Depression of the 1930s, at a time when more than 5,000 banks had failed and thousands of people were out of work. Roosevelt took action. First he declared a bank holiday that closed all the banks so no more could fail; then he reopened the banks little by little with government support. Roosevelt believed in using the full power of government to help what he called the forgotten people. And it was these workers, the wage earners, who felt the strongest affection toward Roosevelt. There were others, however, who felt that Roosevelts policies were destroying the American system of government, and they opposed him in the same intense way that others admired him.In 1940 the Democrats nominated Roosevelt for an unprecedented third term. No president in American history had ever served three terms, but Roosevelt felt an obligation not to quit while the United States entry into World War II was looming in the future. He accepted the nomination and went on to an easy victory.
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After two decades of growing student enrollments and economic prosperity, business schools in the United States have started to face harder times. Only Harvards MBA School has shown a substantial increase in enrollment in recent years. Both Princeton and Stanford have seen decreases in their enrollments. Since 1990, the number of people receiving Masters in Business Administration (MBA) degrees, has dropped about 3 percent to 75,000 and the trend of lower enrollment rates is expected to continue.There are two factors causing this decrease in students seeking an MBA degree. The first one is that many graduates of four-year colleges are finding that an MBA degree does not guarantee a plush job on Wall Street, or in other financial districts of major American cities. Many of the entry-level management jobs are going to students graduating with Master of Arts degrees in English and the humanities as well as those holding MBA degrees. Students have asked the question, Is an MBA degree really what I need to be best prepared for getting a good job? The second major factor has been the cutting of American payrolls and the lower number of entry-level jobs being offered. Business needs are changing, and MBA schools are struggling to meet the new demands.
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Do you have trouble sleeping at night? Then maybe this is for you.When you worry about needing sleep and twist around trying to find a comfortable position, youre probably only making it more difficult to relax.You may also have some bad habits that contribute to the problem. Do you rest frequently during the day? Do you think about sleeping a lot, or sleeping late on weekends? Any or all of these factors might be leading to your insomnia by disrupting your bodys natural rhythms.What should you do then on those sleepless nights? Dont bother with sleeping pills; they can actually cause worse insomnia later. The best thing to do is to drink milk or eat cheese or tuna fish. They are all rich in an amino acid that helps produce in the brain a neurotransmitter that induces sleep. This neurotransmitter will help you relax, and youll be on the way to getting a good nights sleep.
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Langston Hughes was one of the greatest American writers of the twentieth century. He was born in Joplin, Missouri, and moved to Cleveland at the age of fourteen. Several years later he spent one year in Mexico before attending Columbia University in New York. For a few years after that he roamed the world as a seaman, visiting ports around the world and writing some poetry. He returned to the United States and attended Lincoln University, where he won the Witter Bynner Prize for undergraduate poetry. After graduating in 1928, he traveled to Spain and to Russia with the help of a Guggenhein fellowship. His novel include Not Without Laughter(1930) and The Big Sea(1940). He wrote an autobiography in 1956 and also published several collections of poetry. The collections include The Weary Blues(1926), The Dream Keeper(1932), Shakespeare in Harlem(1942), Fields of Wonder(1947), One way Ticket(1947), and Selected Poems(1959). A man of many talents, Hughes was also a lyricist, and a journalist. As an older man in the 1960s he spent much of his time collecting poems from Africa and from African-Americans to popularize black writers. Hughes is one of the most accomplished writers in American literary history, and he is seen as one of the artistic leaders of the Harlem Renaissance, the period when a neighborhood that was predominantly black produced a flood of great literature, music, and other art forms depicting daily city life for African-Americans.
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A pilot cannot fly a plane by sight alone. In many conditions, such as flying at night and landing in dense fog, a pilot must use radar, an alternative way of navigating. Since human eyes are not very good at determining speeds of approaching objects, radar can show a pilot how fast nearby planes are moving. The basic principle of radar is exemplified by what happens when one shouts in a cave. The echo of the sounds against the wall helps a person determine the size of the cave. With radar, however, the waves are radio waves instead of sound waves. Radio waves travel at the speed of light, about 300,000 kilometers in one second. A radar set sends out a short burst of radion waves. Then it receives the echoes produced when the waves bounce off objects. By determining the time it takes for the echoes to return to the radar set, a trained technician can determine the distance between the radar set and other objects. The word radar, in fact, gets its name from the term radio detection and ranging. ranging is the term for detection of the distance between an object and the radar set. Besides being of critical importance to pilots, radar is essential for air traffic control, tracking weather systems and storms.
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Alzheimers disease impairs a persons ability to recall memories, both distant and as recent as a few hours before. Although there is not yet a cure for the illness, there may be hope for a cure with a protein called nerve growth factor. The protein is produced by nerve cells in the same region of the brain where Alzheimers occurs. Based on this relationship, scientists from the University of Lund in Sweden and the University of California at San Diego designed an experiment to test whether doses of nerve growth factor could reverse the effects of memory loss caused by Alzheimers. Using a group of rats with impaired 奥鹏华中师范大学平时在线作业memory, the scientists gave half of the rats doses of nerve growth factor while giving the other half a blood protein as a placebo, thus creating a control group. At the end of the four-week test, the rats given the nerve growth factor performed equally to rats with normal memory abilities. While the experiments do not show that nerve growth factor can stop the general process of deterioration caused by Alzheimers, they do show potential as a means to slowing the process significantly.
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Carbohydrates, which are sugars, are an essential part of a healthy diet. They provided the main source of energy for the body, and they also function to flavor and sweeten foods. Carbohydrates range from simple sugars like glucose to complex sugars such as amylose and amylopection. Nutritionists estimate that carbohydrates should make up about one-fourth to one-fifth of a persons diet. This translates to about 75-100 grams of carbohydrates per day.A diet that is deficient in carbohydrates can have an adverse effect on a persons health. When the body lacks a sufficient amount of carbohydrates it must then use its protein supplies for energy, a process called gluconeogenesis. This, however, results in a lack of necessary protein, and further health difficulties may occur. A lack of carbohydrates can also lead to ketosis, a build-up of ketones in the body that causes fatigue, lethargy and bad breath.
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Some doctors write neatly and clearly, but most doctors do not. They write very quickly and untidily. Druggists have lots of practice in reading doctors notes, but some times doctors write so badly that even the druggist cannot read them.One day a lady wrote a letter to a doctor inviting him to have dinner at her house. The doctor wrote a reply, but he wrote so carelessly that the lady could not read it.What shall I do? she said to her husband anxiously. I dont know if he is going to come or not. And I dont want to phone him and say that I cant read his writing.Her husband frowned thoughtfully. Then he had an idea.Take it to the druggist, he said. He will be able to read it easily.Thank you, said the wife gratefully. Thats a very good idea.She went to the drugstore and gave the doctors note to the druggist. The druggist looked at it very carefully. Then he got his glasses and looked at the note more closely.Could you wait a moment, Madam? he said politely. He went to the back of his store. After a few minutes he returned, smiling cheerfully and carrying a large bottle. He gave the bottle to the lady.Take one spoonful before every meal. he said.
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Martin Luther King, Jr., is well known for his work in civil rights and for his many famous speeches. Among them his moving I have a dream speech. But fewer people know much about Kings childhood. M. L., as he was called, was born in 1929 in Atlanta, Georgia, at the home of his maternal grandfather. M. L.s grandfather, the Reverend A.D. Williams, purchased their home on Auburn Avenue in 1909. twenty years before M.L. was born. The Reverend Williams, an eloquent speaker, played an important role in the community since so many peoples lives centered around the church. He allowed his church and his home to be used as a meeting place for a number of organizations dedicated to the education and social advancement of blacks. M.L. grew up in this atmosphere, with his home being used as a community gathering place, and was no doubt influenced by it.M.L.s childhood was not especially eventful. His father was a minister and his mother was a musician. He was the second of three children, and he attended all-black schools in a black neighborhood. The neighborhood was not poor, however. Auburn Avenue was the main artery through a prosperous neighborhood that had come to symbolize achievement for Atlantas black people. It was an area of banks, insurance companies, builders, jewelers, tailors, doctors, lawyers, and other black-owned of black-operated businesses and services. Even in the face of Atlantas segregation, the distinct thrived. Dr. King never forgot the community spirit he had known as a child, nor did he forget the racial prejudice that was a seemingly insurmountable barrier that kept black Atlantans from mingling with whites.
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