3. A low-pressure weather system is approaching Plainville; rainfall results from about 70 percent of such systems in the Plainville area. Moreover, the current season, spring, is the time of year in which thundershowers, which sometimes result from low-pressure systems, are most likely to occur in Plainville.

　　Knowing which one of the following, in addition to the information above, would be most useful for determine the probability that Plainville will have a thundershower soon?

　　A. the percentage of thundershowers in Plainville that occur in the spring

　　B. the percentage of spring rainfalls in Plainville that are thundershowers

　　C. the percentage of thundershowers in Plainville that result from low-pressure systems

　　D. whether low-pressure systems in other areas are associated with rainfall

　　E. whether Plainville has more or fewer thundershowers each spring than do near by towns

　　参考答案：C

　　思路：文中给出两个条件，1是低压天气将到达，而70%的低压天气导致降雨，2是现在正是1年中雷阵雨最多的季节且雷阵雨有时也是由于低压天气导致;答案(C)给出了低压天气导致雷阵雨的比率，用70%乘以这个比率，就可以得到下雷阵雨的概率了。

　　A、B没能和低压天气联系起来，D、E为无关选项

　　4. More than a year ago, the city announced that police would crack down on illegally parked cars and that resources would be diverted from writing speeding tickets to ticketing illegally parked cars. But no crackdown has taken place. The police chief claims that resources have had to be diverted from writing speeding tickets to combating the city’s staggering drug problem. Yet the police are still writing as many speeding tickets as ever. Therefore, the excuse about resources being tied up in fighting drug-related crime simply is not true.

　　The conclusion in the passage depends on the assumption that

　　A. every member of the police force is qualified to work on combating the city’s drug problem

　　B. drug-related crime is not as serious a problem for the city as the police chief claims it is

　　C. writing speeding tickets should be as important a priority for the city as combating drug-related crime

　　D. the police could be cracking down on illegally parked cars and combating the drug problem without having to reduce writing speeding tickets

　　E. the police cannot continue writing as many speeding tickets as ever while diverting resources to combating drug-related crime

　　参考答案：E

　　思路：结论是由于对超速行驶开出的罚单并未减少，所以资源并未转移，其逆否命题则是，资源如果真的转移，罚单一定减少，也就是E指出的 — 罚单不可能与原来一样多。

　　5. A gas tax of one cent per gallon would raise one billion dollars per year at current consumption rates. Since a tax of fifty cents per gallon would therefore raise fifty billion dollars per year, it seems a perfect way to deal with the federal budget deficit. This tax would have the additional advantage that the resulting drop in the demand for gasoline would be ecologically sound and would keep our county from being too dependent on foreign oil producers.

　　Which one of the following most clearly identifies an error in the author’s reasoning?

　　A. The author cites irrelevant data.

　　B. The author relies on incorrect current consumption figures.

　　C. The author makes incompatible assumptions.

　　D. The author mistakes an effect for a cause.

　　E. The author appeals to conscience rather than reason.

　　参考答案：C

　　思路：作者得出的结论有两个，1是提高汽油税率，可以同比提高税收所得，这一结论的前提条件是，汽油的消费量不受税率影响;2是提高税率可以降低对汽油的消费需求，这一结论的假设条件与前一结论的假设条件是互相矛盾的，因此显而易见，C正确。

　　6. The axis of Earth’s daily rotation is tilted with respect to the plane of its orbit at an angle of roughly 23 degrees. That angle can be kept fairly stable only by the gravitational influence of Earth’s large, nearby Moon. Without such a stable and moderate axis tilt, a planet’s climate is too extreme and unstable to support life. Mars, for example, has only very small moons, tilts at wildly fluctuating angles, and cannot support life.

　　If the statements above are true, which one of the following must also be true on the basis of them?

　　A. If Mars had a sufficiently large nearby moon, Mars would be able to support life.

　　B. If Earth’s Moon were to leave Earth’s orbit, Earth’s climate would be unable to support life.

　　C. Any planet with a stable, moderate axis tilt can support life.

　　D. Gravitational influences other than moons have little or no effect on the magnitude of the tilt angle of either Earth’s or Mars’s axis.

　　E. No planet that has more than one moon can support life.