托福听力之原文演讲听写(4)

　演讲听写训练 1

　　By the end of the term I hope you'll be convinced as I am that formal writing always requires revision. Sometimes it requires a fairly major rewriting of the paper. Some students may have the mistaken idea that revision means simply making corrections in spelling and grammar. I call that proofreading. What I expect you to do is you revise, is to evaluate and improve the overall effectiveness of your paper. But how can you tell if your paper is effective? Well, for example, start by asking yourself these questions: Is the topic restricted enough to be fully discussed within the given links? Are the main ideas clear? Are they supported by the specific details in the examples? Do they move smoothly from one idea to the next? You'll need enough time for a possible major overhaul, that is, you may have to make a lot of changes before your paper becomes really clear to the reader. So I'll expect a preliminary draft of each paper two weeks before the final due date. That way I can critisize it and get it back in time for you to revise it. Then you can submit it a final draft for grading. This process may seem like a great deal of trouble at first but I think you will find it valuable. In fact after you finish this course I doubt that you will ever turn in a term paper without first revising it carefully.

　　演讲听写训练 2

　　Our electric car is the way of the future. Automobile manufactures are under the pressure to develop cars that do not pollute. One powerful motive is a California law requiring that by the year 2000 10% of the new car sales in the state be so-called zero emission vehicles. These cars must put no pollutants whatsoever into the atmosphere. California is a huge market for the automobile companies. So they are working hard to meet this standards. So far the electric car seems to be the best alternative.  So the biggest advantage of electric cars is that they don't pollute. However they will be in competition with gas powered cars . And that's where the witnesses come out. The big problem is that the batteries in electric cars weigh a lot relative to the amount of power they deliver. For instance in one electric car the batteries weigh four hundred kilograms and they provide enough energy to go 250 km before recharging, which take 8 hours. Compare that to a moderately fuel-efficient conventional car it can go 400-700 km on a tank of gas. And refilling takes just minutes. If there are other drains on an electric car's batteries besides a motor, headlights, air-conditioning or a heater, its already limited range would be significantly reduced. So automobile engineers are trying to make more powerful batteries that would increase the car's range and make them more attractive to buyers.

　　演讲听写训练 3

　　I'd like to welcome you all to the museum of natural history. Today's tour will take us through our newly-renovated dinosaur exhibit, where we have the largest collection of dinosaur fossils anywhere in the world. Before we begin the tour let me mention that there have been some major modifications to some of the exhibits over the past three years. Basically these changes were made because of the recent changes in the way scientists interpret dinosaur behavior. For example, when we get to the first room, you will be able to see that tyrannosaurus rex skeleton is no longer standing upright with its tail dragging on the floor. That's because paleontologists, as they examine the area around its footprints more closely, realized they could find no evidence of a heavy dragging tail, which would have left behind marks in the earth. In its new position, the backbone is parallel to the floor, its head is pushed forward and its tail is stretched out acting as a counterweight. This new pose stresses the relationship between dinosaurs and modern birds and supports the theory that dinosaurs are actually more closely related to birds than to any other existing creature. Let me also point out that we have changed the way we group dinosaurs in our displays. There is a new school of thought called kledistics where scientists determine relationships among the animals according to common physical characteristics. The plateosaurus and the ovirapter, for instance, are separated by 148 million years, but they are grouped together here because they both have a grassbean forefoot and its S-shaped neck. Physical evidence that they are indeed related. So now the exhibition halls are arranged more like a family tree rather than the walk-through tine that they used to be.

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