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由于资本利得和再投资收益具有不确定性，投资者在作投资决策时计算的到期收益和到期收益率只是预期的收益和收益率，只有当投资期结束时才能计算实际收益和实际到期收益率。（）
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Sugar is so much a part of our modern life that we only really think about it when, for some reason, we cannot obtain it. It has been known to man for at least 3,000 years, but has come into common use only in modern times. Until quite recently it was considered as a medicine and as a luxury for the very rich only. Sugar is, then, very important to our civilization. But what exactly is it Of course, most of us recognize sugar immediately as the sweet material which we put in coffee or cakes. This common form of sugar is derived from two plants: the sugar cane (a type of grass which grows to a height of twenty feet) and the sugar beet (which grows underground). But there are in fact many types of sugar, and the chemist recognizes hundreds of different varieties, each coming from a different source. About 90% of the sugar produced as food. Only 10% is used in industry for purposes other than food production. Yet sugar has great possibilities for use as the basis of chemicals. It can even be used for making plastics. In the future these potential uses will certainly be developed more than in the past. There are many reasons why we should increase the production of sugar. Most important is that it is one of the most highly concentrated of energy foods. Thus sugar cane and beet produce an average of 7, 000,000 calories per acre. In this way they have the advantage over potatoes which give only 4,000,000, while figure for wheat and beans is 2,000,000 each. So three acres of land growing wheat and potatoes give only slightly more energy than one acre of sugar. The third paragraph emphasizes________.
How Should You Build up Your Vocabulary Exactly what do you do during a normal day How do you spend your time Paul T. Rankin very much wanted an answer to that question. To get it, he asked sixty-eight individuals to keep an accurate, detailed record of what they did every minute of their waking hours. When he consolidated (巩固) his findings, he discovered that the average individual spent 70 percent of his waking time doing one thing only--communication. That meant either reading, writing, speaking or listening. Put that evidence alongside of the research findings uncovered by the Human Engineering Laboratories. In exploring aptitudes and careers involving, among other things, data from 30,000 vocabulary tests given yearly, they discovered that big incomes and big vocabularies go together. Vocabulary, more than any other factor yet known, predicts financial success. And it all fits. Each word you add to your vocabulary makes you a better reader, writer, speaker and listener. Furthermore, linguistic scientists are quick to point out that we actually think with words. If that is so, new words make us better thinkers as well as communicators. No wonder more words are likely to mean more money. What better reason for beginning right now to extend your vocabulary Take reading. What exactly do you read Common sense says you read words. Research confirms that fact. "Vocabulary in context" contributes 39 percent to comprehension. That’’ s more than any other factor isolated and studied--even more than intelligence. And "word discrimination" contributes more to speed of reading than any other factor--28 percent. In short, your efforts to improve vocabulary will pay off in both comprehension and speed. Suppose, as you’’ re reading along, you lumtebs across a strange word. Did you find your self stopping for a closer look at lumtebs Pardon the spelling slip. That’’ s actually the word stumble (偶然发现). The letter just got mixed around. Obviously you now know that strange words do slow you down--or even stop you completely. Furthermore, strange words hinder (妨碍) comprehension. Which is easier to understand, "eschew garrulity" or "avoiding talking too much" What you need is a vital ,dynamic approach to vocabulary building. Hybrid (混合种) corn combines the best qualities of several varieties to ensure maximum productivity. A hybrid approach to vocabulary should, in the same way, ensure maximum results. That’’ s why you should use the CPD formula.Through Context When students in a college class were asked what should be done when they came across an unknown word in their reading, 84 percent said, "Look it up in file dictionary." If you do, however, you short-circuit the very mental processes needed to make your efforts most productive. But there’’ s another reason. Suppose someone asks you what the word fast means. You answer, "speedy or swift". But does it mean that in such contexts as "fast color", "fast woman", or "fast friend" And if a horse is fast, is it securely tied or galloping (飞驰) at top speed It could be either. It all depends. On the dictionary No, on context--on how the word is actually used. After all, there are over twenty different meanings for fast in the dictionary. But the dictionary doesn’’t tell you which meaning is intended. That’’ s why it makes such good sense to begin with context.Through Word Parts Now for the next step. Often unfamiliar words contain one or more parts, which, if recognized, provide definite help with meaning. Suppose you read that someone "had a predilection for reading mysteries". The context certainly isn’’t too helpful. But do you see a prefix, suffix or root that you know Well, there’’ s the familiar prefix pre-, meaning "before’’. Look back at the context and try inserting "before". Reading mysteries apparently comes "before" other kinds of reading. Yes, a predilection--or preference is something put "before" something else. Or take the word monolithic. Try to isolate the parts. There is the prefix mono-, meaning "one", and the root lith, meaning "stone". Finally, there’’ s the suffix -ic, meaning "consisting of". Those three parts add up to this definition: "consisting of one stone".To speed up your use of word parts, you will be introduced to the fourteen most important words in the English language. The prefix and root elements in those few words are found in over 14,000 words of desk dictionary size. With those amazingly useful shortcuts, you can build vocabulary, not a snail’’ s pace, one word at a time, but in giant strides, up to a thou sand words at a time. Your second step, then, is to look for familiar word parts. If they do not give you exact meanings, they should at least bring you much closer.Through the Dictionary Now you can see why you should consult the dictionary last, not first. You’’ve looked carefully at the context. You’’ve looked for familiar word parts. Now you play Sherlock Holmes an exciting role. You hypothesize. In light of context or word parts, you try to solve a mystery. What exactly does that strange word mean Only after you go through the mental gymnastics to come up with a tentative definition should you open the dictionary to see if you’’ re right. After all, those first two steps or approaches spark a stronger than usual interest in that dictionary definition. You’’ re now personally involved. Did you figure out the word meaning Your heightened interest will lead to a better memory of both word and meaning. It also encourages your development of the habits needed to accelerate your progress. And when you see in black and white the definition you had expected, what a feeling of accomplishment is yours. In that way, the CPD Formula provides the exact dynamic interplay of approaches for maximum effectiveness. Well, there it is, your new formula Context, Parts, Dictionary. Use it! The exercises that follow will give you specific, step-by-step help in sharpening your awareness of contextual clues, learning the most useful word parts, and using the dictionary with increased accuracy and ease. The results will be like the money in the bank. This passage is meant to teach readers how to enlarge their vocabularies by means of the CPD Formula.
阅读文字材料，按要求回答36-40题。 长期大量使用化学农药使得抗药害虫种类不断增加，且抗药性也越来越厉害。今天要杀死这些抗药害虫，必须将剂量增加成千上万倍，既增加生产成本，又会杀死害虫天敌，造成农作物害虫频频成灾。尤为严重的是，大量使用化学农药，会加剧环境污染，损害人类身体健康。据联合国环境规划署统计，全世界每年有200万人发生农药急性中毒，其中有四万人丧生。而病得不清不楚，死得不明不白的慢性中毒者，数量无法统计。 面对化学农药长期滥施造成的一系列严重问题，各国科学家从加紧研究有毒植物和推广应用植物农药等方面寻找出路。近年来，植物农药的研制已取得了一定成果。植物农药又叫生物农药，是利用有毒植物中的多种杀虫成分，经过提炼后生产的农药。与化学农药比较，植物农药有着突出的优点。 由于它们的杀虫有效成分为天然物质。而不是人工合成的化学物质。因此，施用后较易分解为无毒物质。对环境无污染。由于植物杀虫剂杀虫成分的多元化，就使害虫较难产生抗药性。这同病菌对中药混合物煎剂较之于单质的抗菌素更难______的道理一样。植物农药有益生物(即害虫天敌)的安全。根据试验，使用我国研制的鱼藤菊酯植物杀虫剂的常用剂量喷施，对蔬菜头号害虫萝卜蚜的防治效果达到99.85%。而对蚜虫天敌瓢虫的杀伤率仅为11.58%；对照使用的化学杀虫剂乐果乳油的两个指标分别为71．5%和28.54%。 此外，有毒植物可以大量种植，而且开发费用也较低。我国已发现的有毒植物达一万多种，它们当中大都具有杀虫抑菌作用，较有价值的杀虫植物大概有五类：对昆虫有强烈驱赶作用的，如丁香、茴香；对作物真菌病和病毒病有疗效的，如大黄、烟草；可提炼使昆虫有强烈拒食作用的天然物质的，如川楝、花椒；能影响昆虫激素平衡的，如万寿菊、香茅；使昆虫绝育的，如喜树硷、姜油等。 对文中“植物农药有着突出的优点”一句的解释不正确的一项是( )。
A 500-year-old world map that was the first to name a newfound continent west of Europe "America" was sold for one million dollars at an auction(拍卖) in Christie’’s in London. Charles Frodshan, a London book and manuscript dealer, bought the map for 545,600 pounds during bidding at Christie’’s. Christie’’s said the map was also the first printed portrayal(肖像图) of the Earth as a globe, the first that distinguishes North and South America individually, and the first complete picture of the Pacific Ocean. Printed in 1507 by the German geographer Martin Waldseemuller, the map is just one of five in existence and had been expected to sell for between 500,000 and 800,000 pounds. The document, which is the most important article in the sale of maps, atlases and globes by Christie’’s, was discovered in February 2003 after a European collector realized that it was one of the maps in his collection. "This is one of the most exciting discoveries of my career, and represents the peak in the history of map making... This simple sheet of paper holds so many new and anticipated discoveries, all created with an enormous leap of faith by a venerable geographer in a small town in Lorraine (eastern France)," said Tom Lamb, director of the auction house’’s book and manuscript department, in a statement. Most history documents credit the Genoa-born explorer, Christopher Columbus, with being the first European to discover the so-called New World of North and South America in 1492, but he was convinced it was part of Asia. A second Italian, Amerigo Vespucci, actually argued that the landmass to the west of Europe was a whole new continent. Until the map’’s publication, the layout of the world had been based on the knowledge of the ancient Greeks. But in 1505, Rene II, the Duke of Lorraine ordered a group of scholars led by Waldseemuller to draft a new world map. He gave them a French translation of Vespucci’’s travels and as a result, the scholars decided to name the new landmass "America" after the traveler’’s first name. In 1492, when Christopher Columbus reached the new continent, he________.
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