【正文】 ty water and then not providing adequate drainage for it will fill the soil with salt, and turn the area into a desert.39. What is the main topic of the talk?40. How is the soil damaged by over cultivation? 41. What is over grazing?42. How does over grazing damage soil?43. According to the speaker, what is the main problem with irrigation? 4447 I’ve mentioned how DNA have solved many mysteries in biology. And today I want to talk about how it might relate to hypothesis about the travels of the green turtle. Every winter some green turtles make a 2000 km journey from Brazil to Ascension Island in the middle of Atlantic, where they mate and lay eggs. But the question is why do they travel so far to lay their eggs? One researcher hypothesized that there are two parts to the explanation. One is natal homing, the instinct that drives green turtles to always return to the beach where they were hatched. The second part has to do with continental drift, the theory that the positions of earth continents have changed considerably overtime. Brazil and Ascension Island were once much closer together, and continental drift drove them apart. But the turtles kept on going back to the island where they hatched. However another scientist question this explanation on the ground that it would be very unlikely that conditions would allow generations of turtles over hundreds of millions of years to keep going back to the same nesting ground every single year. So, what is the connection to DNA? Well, there are groups of green turtles that nest in locations other than the Ascension Island. If green turtles always return to the place where they were hatched, then the turtles that have been going to the Ascension Island to nest would’ve been genetically isolated long enough to have DNA that was very different from the green turtles that nest else where. But when scientists examine DNA from these turtles, their DNA wasn’t that different from the DNA of the turtles that go to Ascension Island. Do you have a shock? Well, we still don’t know the answer to the question about why a certain group of turtles go to Ascension Island, but this study was a nice example of the usefulness of DNA analysis to biology.44. What does the Prof mainly discuss?45. What do green turtles do when they get to Ascension Island?46. According to one hypothesis, why do green turtles go to Ascension Island?47. How is DNA used in research on green turtles?4850As I am sure you are aware, history is full of people who were so admired that over the centuries they bee almost mythical（神秘的）figures. George Washington is a good example. Everyone knows this story about his chopping down the cherry tree when he was young and bravely confessing to his mischief later. People greatly admired Washington’s integrity. And so, out of that, this story evolved, even though no one knows for sure whether the incident ever occurred. Then there is the American Indian, Poke Hunters, beloved by history for making peace between the English Colonies and the American Indians. The history of her life has also bee somewhat mythical. At the historical society exhibit next week, we’ll see many artistic works depicting the major events of her life. And while we are there, keeping in mind that much of what you’ll see in the paintings reflects how much she was admired, but not necessarily the fact of her life. For instance, one painting shows her saving the life of Jon Smith, an English Colonist, who had been captured by her tribe. Smith, so the story goes, was about to be executed when twelveyearsold Poke Hunters lay her head on top of his. Tells you a lot about her courage. But Jon Smith himself related this story only years after Poke Hunters had bee famous, which suggests that he may have embellished（修飾）the truth a little bit, as many of the works that we’ll see in next week may have done. Something else to remember: paintings portrait her physical appearance in many different ways, but always flattering ways. Yet only one picture of her was ever painted while she was living. 48. Why does the speaker mention the story about George Washington and the cherry tree?49. According the speaker, why is Poke Hunters famous? 50. What does the speaker imply about most of the paintings of Poke Hunters?03年 8月 托福聽力文字2 B or not 2 B! 注：這句話比較猛，建議在聽力錯題突破20時酌情使用^^Part A1. M: How’s that project to your economics class ing along?W: I just put the finishing touches on（進(jìn)入最后階段）this morning.Q: What does the woman mean? 2. W: You are such a good listener. What’s your secret? M: Well, when you grow up sharing a room with three older brothers, he get plenty of practice. Q: What can be inferred about the man?3. M: Didn’t Mary invite you to e with us to the movies tonight?W: she did. But I told her no. I didn’t like that movie the first time around（那電影第一次上映時，我就不大喜歡）.Q: What can be inferred about the woman? 4. W: This rash（皮疹）on my arm is driving me crazy. What do you think it could be?M: I really couldn’t say for sure, but it looks like something you ought to have checked out.Q: What does the man imply the woman should do?5. W: Jim, have you seen the photos from Rachel’s party? There is a really funny one of you dancing in the living room.M: Oh, yeah, that one. I don’t think I’ll ever live it down（使人忘記過失）. Q: What does the man mean?6. M: It’s been hot and humid for three weeks straight(一直). I wish it’d light up.W: I love summer weather, but there is a limit. Q: What does the woman mean?7. W: You probably shouldn’t keep the clothes in the drier for longer than 45 minutes. M: Oh, no, I’ve already had them in there for an hour.Q: What will the man probably do next?8. W: Is it too late for me to withdraw from my music class?M: Um, not that I know of.Q: What does the man mean? (know of : be slightly acquainted with)9. M: Thank goodness spring break starts next week. Are you doing anything spe