LSAT真题详解(官方解释)Section 1.docx

LSAT真题详解(官方解释)Section 1Section 1 Time35 minutes 25 Questions 1. Sea turtle hatchlings leaving their hatching grounds onFloridabeaches reach ocean currents by swimming to the northeast, as defined by the north of the Earths magnetic field.Floridahatchlings placed in a large indoor tank also swim toward the northeast. But when the tank is surrounded by an artificial magnetic field twice as strong as the Earths field and opposite in direction, the hatchlings swim in the direction opposite to that in which they swim without the artificial magnetic field. The information in the statements above most strongly supports which one of the following? (A) Once baby sea turtles reach the open sea, they join groups of adults in theNorth Atlantic. (B) The direction in which ocean currents flow is determined by the magnetic field of the Earth. (C) Baby sea turtles are able to sense the magnetic field of the Earth. (D) No sea turtle ever returns to the beach where it hatched. (E) If a sea turtle hatches on the coast ofAfrica, it will swim toward the southwest. General Description: This question asks you to draw an inference based on the information presented. It is not enough that a response be true, if the information in that response is irrelevant to the information presented. Nor is it sufficient that a response present information that is merely consistent with the information presented in the passage; the best answer must present information that is supported by the information in the passage. A. Incorrect. Since the passage does not say anything about adult sea turtles, or about the location of the adults, this claim is not supported by information in the passage. B. Incorrect. The passage does not provide any information about the relation between ocean currents and the magnetic field of the Earth, and so this response is not correct. C. Correct. Though the passage does not draw the conclusion that baby sea turtles can sense the magnetic field, the fact that the hatchling change their direction certainly suggests that the hatchlings are responding to changes in the magnetic field. And if the hatchlings respond to the changes, then on reasonable inference is that they are able to sense the magnetic field. So, this is the best answer. D. Incorrect. The information in the passage about the behavior of sea turtle hatchlings in the wild deals only with their behavior as they leave their hatching grounds. It provides no support for a claim about the sea turtles behavior after they have left their hatching rounds. E. Incorrect. The passage does not provide any information that would justify an inference about the behavior of hatchlings on the coast ofAfrica. Difficulty Level: Easy Tips and Pitfalls: Read questions carefully. If a question asks which statement is supported by the passage, do not choose a response just because it seems on independent grounds to be plausible or likely-you must pick a response based on the information given in the passage. Question 2-3 Twenty percent of the population of Springhill has been toItalyat least once in the last five years, and thirty percent of the population of Springhill has been toFranceat least once in the last five years. Therefore, half of the population of Springhill has been toEuropeat least once in the last five years. 2. The argument is faulty because it ignores the possibility that (A) some of the population of Springhill has been neither toItalynor toFrancein the last five years. (B) some of the population of Springhill has been both toItalyand toFrancein the last five years. (C) some of the population of Springhill has been either toItalyor toFrancein the last five years, but not to both. (D) none of the population of Springhill has been to any country inEuropeother thanItalyorFrancein the last five years. (E) none of the population of Springhill has been either toItalyor toFrancemore than once in the last five years. General Description: This question asks you to identify the logical problem in an argument caused by failure to consider a logically relevant possibility. The best answer, then, will not merely present some possibility the argument fails to consider. Rather, it will be something the argument should have considered: a possibility that, if it turned out to be true, would tend to undermine the reasoning leading to the arguments conclusion. A. Incorrect. It would not make the argument flawed to have ignored this possibility: the arguments conclusion is consistent with the possibility that the other half of Springhills population has never been toEuropeat all. Because the conclusion is consistent with this possibility, the argument does not need to address it. B. Correct. If there were no overlap between the travelers to Italy and the Travelers to France, then the arguments premises would provide good evidence for its conclusion: 20%+30%=50%. But the argument has presented no reason to suppose that there is no such overlap, and to the extent that there is, the argument is undermined. That is, if some people are counted both in theItalygroup and in theFrancegroup, then the two groups together do not add up to 50%. (B) describes just this problem and is the best answer. C. Incorrect. Far from ignoring this possibility, the argument seems to be assuming that it is actual. In fact, the greater the number of people from Springhill who have been toItalyor toFrancein the last five years, but not to both, the stronger the argument. D. Far from ignoring this possibility, the argument seems to be assuming that it is actual. For if there were people FORM Springhill who had been to other European countries in the last five years, the argument would be stronger for mentioning them. E. Incorrect. The argument is not faulty in ignoring this possibility, because it is irrelevant: The argument is about numbers of people who have been toItalyand/orFrance(and thusEurope) at least once in the last five years. Difficulty Level: Easy Tips and Pitfalls: Though answering LSAT questions does not require perFORMing any mathematical calculations, the questions do assume a college-level understanding of concepts that may be termed “mathematical,” including “percent.” 3. McBrides and Leggetts statements commit them to disagreeing about the truth of which one of the following? (A) The manufacture of full-size cars should be discouraged. (B) Fuel conservation is less important than safety in case of a collision. (C) When a full-size car and a subcompact car collide, the occupants of the full-size car are less likely than the occupants of the subcompact car to be seriously injured. (D) Reducing the number of full-size cars on the highway will reduce the frequency of collisions between automobiles. (E) The new fuel-efficiency standards will encourage automobile manufacturers to build more subcompact cars. General Description: Since the question asks you to determine a point of disagreement between McBride and Leggett, the best answer will be the on describing a point that McBride accepts and Leggett rejectsor vice versa. A. Correct. McBride opposes the introduction of fuel-efficiency standards precisely because these standards will discourage the manufacture of full-size cars, calling that prospect “troubling.” So McBride would disagree with (A). Leggett, on the other hand, explicitly disagrees with McBrides position, arguing that the standards ought to be supported precisely because they discourage the manufacture of full-size cars and thus agreeing with (A). Thus, (A) is the best answer. B. Incorrect. Though McBride and Leggett disagree about whether the standards should be implemented, both clearly are interested in the issue of safety, and it is quite plausible that one or both believe that fuel conservation is less important than is safety. However, this can be the best answer only if there is evidence that either Leggett or McBride believes that fuel conservation is not less important than is safety; the passage, however, provides no grounds for such an inference. C. Incorrect. The passage does not provide enough information to judge whether McBride and Leggett disagree on this point. McBrides comments suggest agreement with it, but it is not clear where Leggett stands on the claim in question. Leggett says only that it is more likely that someone will be seriously injured in a collision if one of the cars is full-size, without specifying the location of the injured person. D. Incorrect. Neither Leggett nor McBride mentions anything about the frequency of accidents; both are more concerned with the likelihood of harm should be accident occur. E. Incorrect. Both Leggett and McBride agree that the new fuel-efficiency standards will discourage automobile manufacturers from building full-size cars. However, it is not clear that either believes that the standards will encourage the manufacture of more subcompact cars (as opposed to some third kind of car). Further, even if it is true that the reduction in full-size cars causes an increase in the manufacture of subcompact cars, this is a point of agreement, not disagreement, between Leggett and McBride. Of those who answered this question incorrectly, the majority chose (E), perhaps confusing the issue of whether manufacturers should be encouraged to build more subcompact cars with the issue of whether they will be encouraged to do so. Difficulty Level: Difficult Tips and Pitfalls: When asked to determine a point on which two speakers are committed to agreement or disagreement, be sure to narrow your focus to explicit assertions by the speaker; avoid the temptation to speculate about what (elst) either speaker might believe.4. Which one of the following argumentative strategies does Leggett use in attempting to refute McBrides position? (A) demonstrating that McBrides claims are contradictory (B) challenging the unstated assumption that all cars are either full-size or subcompact (C) shifting the perspective from which the issue of automobile safety is considered (D) raising doubts about the accuracy of a generalization made by McBride (E) demonstrating that it is impossible to follow the course of action advocated by McBrideGeneral Description: This question asks you to find the description of strategy used by Leggett in arguing against McBride. A. Incorrect. McBrides and Leggetts conclusions contradict one another, but there is no suggestion that McBrides statements themselves contradict one another. B. Incorrect. Though the discussion focuses only on full-size and subcompact cars, neither party is presuming that all cars are either full-size or subcompact. C. Correct. From McBrides perspective, discouraging the manufacture of full-size cars is a bad thing, because McBride is considering the relative safety of a collision of two full-size cars and a “mixed” collision involving one full-size and one subcompact car. Leggett is shifting the perspective: Instead of comparing a mixed collision to a collision of two full-size cars, Leggett compares a two-car collision involving a full-size car to a collision of two subcompact cars. From that perspective, discouraging the manufacture of full-size cars is a good thing, because a collision of two subcompact cars is sager than a collision involving a full-size car. The two agree that the new fuel-efficiency standards will discourage the manufacture of full-size cars, but take different perspectives on the implication of that for automobile safetyand so reach opposite conclusions about whether the new standards should be supported. D. Incorrect. Leggett is raising doubts only about the conclusion McBride draws from the evidence, and that conclusion is “The new fuel-efficiency standards should therefore be opposed,” which is not a generalization. This was the most popular incorrect answer. E. The “course of action advocated by McBride” is to oppose the new fuel-efficiency standards. Leggett is simply arguing in favor of supporting them, not claiming that is impossible take McBrides course. Difficulty Level: Difficult Tips and Pitfalls: In answering questions about “argumentative strategy,” it is imperative that you understand the structure of the argument in question. You also need to be able to compare the strategies described in the responses to the argument structure in the passage: If the responses strategy cannot be mapped exactly onto the argument structure, that response is not the best answer.5. Concerns for the environment have led chemists to develop plastics that are degradable. All degradable plastics, which are potentially useful packaging materials, need just the right conditions to break down. Some need exposure to sunlight, some need to be buried in soil and some need to be submerged in water. It should be cautioned that some degradable plastics leave residues of unknown toxicity. If all of the statements above are true, which one of the following must also be true? (A) Some materials that are potentially useful for packaging leave residues of unknown toxicity. (B) Some degradable plastics need both sunlight and submersion in order to break down. (C) Some materials that need sunlight in order to break down are not potentially useful packaging materials. (D) Some materials that leave residues of unknown toxicity are not degradable plastics. (E) Some materials that need to be buried in soil to break down leave residues of unknown toxicity. General Description: This question asks you to determine which one of the responses must be true, given the info in the passage. This is a very strong requirement. It may be easier to think of the task at determining which choice cannot be false, if the statements in the passage are true. Then you can rule out any choice that could be false. A. Correct. Since the passage tells us that all degradable plastics are potentially useful packaging materials, and also that some degradable plastics leave residues of unknown toxicity, it is necessarily true that some potentially useful packaging materials (namely, those degradable plastics) leave residues of unknown toxicity. This is the best answer. B. Incorrect. Thought it is possible that some plastics would need both sunlight and submersion in order to decompose, the passage merely states that at least one is necessary. So, contrary to (B) it is quite possible that only sunlight or submersion is needed, and thus it is quite possible that (B) is false. C. Incorrect. The passage focuses solely on the status of degradable plastics. However, it is quite possible that there are some other materials-that is, nonplastic materials-that need sunlig