一、阅读理解 Until recently astronomers have been puzzled by the fate of red giant and supergiant stars. When the core of a giant star whose mass surpasses 1.4 times the present mass of our Sun (M⊙) exhausts its nuclear fuel, it is unable to support its own weight and collapses into a tiny neutron star. The gravitational energy released during this implosion of the core blows off the remainder of the star in a gigantic explosion, or a supernova. Since around 50 percent of all stars are believed to begin their lives with masses greater than 1.4M⊙, we might expect that one out of every two stars would die as a supernova. But in fact, only one star in thirty dies such a violent death. The rest expire much more peacefully as planetary nebulas. Apparently most massive stars manage to lose sufficient material that their masses drop below the critical value of 1.4 M before they exhaust their nuclear fuel. Evidence supporting this view comes from observations of IRC+10216, a pulsating giant star located 700 light-years away from Earth. A huge rate of mass loss (1 M every 10,000 years) has been deduced from infrared observations of ammonia (NH3) molecules located in the circumstellar cloud around IRC+10216. Recent microwave observations of carbon monoxide (CO) molecules indicate a similar rate of mass loss and demonstrate that the escaping material extends outward from the star for a distance of at least one light-year. Because we know the size of the cloud around IRC+10216 and can use our observations of either NH3 or CO to measure the outflow velocity, we can calculate an age for the circum-stellar cloud. IRC+10216 has apparently expelled, in the form of molecules and dust grains, a mass equal to that of our entire Sun within the past ten thousand years. This implies that some stars can shed huge amounts of matter very quickly and thus may never expire as supernovas. Theoretical models as well as statistics on supernovas and planetary nebulas suggest that stars that begin their lives with masses around 6 M shed sufficient material to drop below the critical value of 1.4M⊙.IRC+10216, for example, should do this in a mere 50,000 years from its birth, only an instant in the life of a star. But what place does IRC+10216 have in stellar evolution? Astronomers suggest that stars like IRC+10216 are actually ― protoplanetary nebulas — old giant stars whose dense cores have almost but not quite rid themselves of the fluffy envelopes of gas around them. Once the star has lost the entire envelope, its exposed core becomes the central star of the planetary nebula and heats and ionizes the last vestiges of the envelope as it flows away into space. This configuration is a full-fledged planetary nebula, long familiar to optical astronomers.
1. The primary purpose of the passage is to ______.
A.offer a method of calculating the age of circum-stellar clouds
B.describe the conditions that result in a star's expiring as a supernova
C.discuss new evidence concerning the composition of planetary nebulas
D.explain why fewer stars than predicted expire as supernovas
A B C D
D
[解析] 意图题。题目问本文的主要目的是什么。第三段第二句提到了计算饶星云年龄的方法，但只是分析问题时的一个步骤，并非文章意图，故A错；由第二段第一句可知，恒星变成超行星只是极少数，因此B项错；第三段最后两句提到了行星状星云，但统计相关数据是为了证明质量在6米左右的恒星，其初始质量足以降至1.4米⊙的临界值以下，故C项错。文章第一段首先介绍了天文学家关于超巨星命运的困惑和超巨星是如何坍缩的；第二段提出了他们消亡于超新星的假设，通过随后的转折“But in fact, only one star in thirty dies such a violent death.The rest expire much more peacefully as planetary nebulas.”以及后面通篇举的例子就是为了说明为什么比预测的更少的恒星会成为超新星，故答案选择D。
2. The view mentioned in the middle of the second paragraph serves to ______.
A.reconcile seemingly contradictory facts
B.undermine a previously held theory
C.take into account data previously held to be insignificant
D.resolve a controversy
A B C D
A
[解析] 结构题。题目问第二段中间部分的观点是为了什么。第二段中间部分为 we might expect that one out of every two stars would die as a supernova. But in fact, only one star in thirty dies such a violent death. The rest expire much more peacefully as planetary nebulas. Apparently most massive stars manage to lose sufficient material that their masses drop below the critical value of 1.4 M before they exhaust their nuclear fuel.因此我们可以预计，每两颗恒星中就有一颗会消亡于超新星。但事实上，每三十颗恒星中只有一颗死得如此惨烈。其余的则以行星状星云的形式平静地消亡。显然，大多数大质量恒星在耗尽核燃料之前都会损失足够多的物质，以至于它们的质 量下降到临界值1.4M以下。A项“调和看似矛盾的事实”，第二段先提出一个观点，接着用实际情况来反驳它，最后提出支持这一论点的证据，因此A项正确；B项“彻底否定之前提出的理论”，说法错误，之前的理论并不算错误，因此这里并不是要彻底否定它，排除；C项“将之前认为无关紧要的数据考虑在内”，偏离文意，排除；D项“解决争议”，这里只是提出新的观点，不是为了解决争议，排除。故答案为A。
3. It can be inferred from the passage that the author assumes which of the following in the discussion of the rate at which IRC+10216 loses mass?______
A.The circumstellar cloud surrounding IRC+10216 consists only of CO and NH3 molecules.
B.The circumstellar cloud surrounding IRC+10216 consists of material expelled from that star.
C.The age of a star is equal to that of its circumstellar cloud.
D.The rate at which IRC+10216 loses mass varies significantly from year to year.
A B C D
B
[解析] 推断题。题目问从文章中可以推断，作者在讨论 IRC+10216的质量损失率时，假设了下列哪个选项?定位在第二段最后一句 A huge rate of mass loss (1 M⊙ every 10,000 years) has been deduced from infrared observations of ammonia (NH3) molecules located in the circumstellar cloud around IRC+10216.(根据红外对 IRC+10216 周围恒星云团中氨(NH3)分子的观测，推断出一个巨大的质量损失率为 1 M⊙/ 10000 年)通过这部分可以合理地推断出“observations of ammonia”是IRC+10216释放出的物质；A错在“only”，根据第三段第二句 Because we know the size of the cloud around IRC+10216 and can use our observations of either NH3 or CO to measure the outflow velocity, we can calculate an age for the circumstellar cloud.可知CO和NH3是研究中用于观测检验的，并不意味着 IRC+10216 周围只有这两种物质。阅读题中，含有绝对意味的选项通常为错误表达，除非文中有同义绝对说法。B为正确答案，根据第三段可知，IRC+10216会向周围排出物质，又根据最后一段的最后两句，一旦这颗恒星失去了整个外壳，它暴露的核心就会成为行星状星云的中心恒星，并在它流向太空时加热和电离外壳的最后残余。这个结构是一个成熟的行星状星云，光学天文学家早就熟悉了。因此IRC+10216周围的环绕恒星云由该恒星喷出的物质组成。C项是根据文章最后一段做出的推断，并不是文中直接举例，排除；根据第二段最后一句，可知质量损失率恒为1M⊙/10000年，D项说每年都有很大变化，说法错误。故答案选择B。
4. According to information provided by the passage, which of the following stars would astronomers most likely describe as a planetary nebula?______
A.A star that began its life with a mass of 5.5 M, has exhausted its nuclear fuel, and has a core that is visible to astronomers.
B.A star that began its life with a mass of 6 M, lost mass at a rate of 1 M per 10,000 years, and exhausted its nuclear fuel in 40,000 years.
C.A star that has exhausted its nuclear fuel, has a mass of 1.2 M, and is surrounded by a circumstellar cloud that obscures its core from view.
D.A star that began its life with a mass greater than 6 M, has just recently exhausted its nuclear fuel, and is in the process of releasing massive amounts of gravitational energy.
A B C D
A
[解析] 推断题。定位在最后一段第三句 Once the star has lost the entire envelope, its exposed core becomes the central star of the planetary nebula and heats and ionizes the last vestiges of the envelope as it flows away into space.(一旦这颗恒星失去了整个外壳，它暴露的核心就会成为行星状星云的中心恒星，并在它流向太空时加热和电离外壳的最后残余)，故A项正确；B 项衰减后的恒星质量没有低于1.4M，不符合条件，错误；C项错在最终云团遮住了核心，不符合条件；D项说该恒星正在释放大量引力能，尚未完成，也不符合条件；故答案选择 A。
5. Which of the following statements would be most likely to follow the last sentence of the passage?______
A.Supernovas are not necessarily the most spectacular events that astronomers have occasion to observe.
B.Apparently, stars that have a mass of greater than 6 M are somewhat rare.
C.Recent studies of CO and NH3 in the circumstellar clouds of stars similar to IRC+10216 have led astronomers to believe that the formation of planetary nebulas precedes the development of supernovas.
D.It appears, then, that IRC+10216 actually represents an intermediate step in the evolution of a giant star into a planetary nebula.
A startup company in California is using machine learning and artificial intelligence to advise fire departments about how to plan for earthquakes and respond to them. The company hopes its algorithms can take a lot of the guesswork out of the planning process for disaster response by making accurate predictions about earthquake damage. It's one of a handful of companies rolling out artificial intelligence and machine learning systems that could help predict and respond to floods, cyber-attacks and other large-scale disasters. Nicole Hu, the company's chief technology officer, says the key is to feed the computers three main categories of data. The first is data about homes and other buildings, such as what materials they're made of, when they were built and how likely they are to collapse when the ground starts shaking. The next category is data about the natural environment. For example, "What is the soil like? What is the elevation like? What is the general humidity like?" explains Hu. "The third thing we look at is live instant data," she says, such as the magnitude of the quake, the traffic in the area of the quake and the weather at the time of the quake. The computer uses the information to make predictions about what would happen if an earthquake occurred in a particular area. It then uses data from past earthquakes to see whether its predictions are any good, and revises its predictive models accordingly. In other words, it learns as it goes, which is basically how machine learning works. Stanford University earthquake engineer Gregory Deierlein consulted for the company.He says one of the most remarkable things about the company's software is its ability to incorporate data from an earthquake as it's happening, and to adjust its predictions in real time. "Those sort of things used to be research projects." says Deierlein. "After an event, we would collect data and a few years later we'd produce new models." Now the new models appear in a matter or minutes. He notes the company's exact methods are opaque. "Like many startup companies they're not fully transparent in everything they're doing," he says. "I mean, that's their proprietary knowledge that they're bringing to it." Nonetheless, some first responders are already convinced the software will be useful. Fire chief Dan Ghiorso leads the Woodside Fire Protection District near San Francisco, which covers about 32 square miles. The San Andreas fault is only a couple hundred feet behind the firehouse. Ghiorso says in the past, when an earthquake hit, he'd have to make educated guesses about what parts of his district might have suffered the most damage, and then drive to each place to make a visual inspection. He hopes the company's software will change that, although he has yet to put it to the test during an actual quake. "Instead of driving thirty-two square miles, in fifteen minutes on a computer I can get a good idea of the concerns," he says. "Instead of me, taking my educated guess, they're putting science behind it, so I'm very confident." Unfortunately, it's going to take a natural disaster to see if his confidence is justified.
6. What can be the best title of the passage?______
A.Causes of Naturally Occurring Earthquakes.
B.Comparing Different Earthquake-Predicting Software.
C.Using Artificial Intelligence To Guide Earthquake Response.
D.Challenges For Making Accurate Predictions about Earthquakes.
7. What is NOT needed for training the earthquake-predicting software?______
A.Data about the buildings.
B.Data about human impacts.
C.Data about past earthquakes.
D.Data about the geographic conditions.
A B C D
B
[解析] 细节题。该题需根据选项定位到文章第二段，该段提到：该公司首席技术官Nicole Hu表示，关键是为电脑提供三大类数据。第一类是关于房屋和其他建筑的数据，比如它们是用什么材料建造的，是什么时候建造的，以及当地面开始晃动时，它们倒塌的可能性有多大。第二类是关于自然环境的数据，比如土壤是什么样的，海拔是多少，一般的湿度是什么样的。第三类则是实时数据，比如地震的震级、地震地区的交通状况以及地震发生时的天气。选项A“关于建筑的数据”属于第一类；选项C“关于过去地震的数据”出现在第二段倒数第二句It then uses data from past earthquakes to see whether its predictions are any good，所以这类数据也是需要的；选项D“关于地理条件的数据”属于第二类。只有B选项文中未提及，故答案选B。
8. What can we learn about the earthquake-predicting software?______
A.Its algorithms have made known to the public.
B.It can measure and locate earthquakes efficiently.
C.It can incorporate live instant data to adjust its predictions.
D.It has proved to be useful in Woodside Fire Protection District.
A B C D
C
[解析] 细节题。根据第三段第二句...one of the most remarkable things about the company's software is its ability to incorporate data from an earthquake as it's happening, and to adjust its predictions in real time.可知该公司的软件最引人注目的一点是，它能够在地震发生时整合地震数据，并实时调整预测。所以C选项表述与原文意思相符，其中live instant data(实时数据)是对原文 data from an earthquake as it's happening 的同义表述；由最后一段首句 Nonetheless, some first responders are already convinced the software will be useful.可知有些人相信该公司的软件是有用的；再根据下文 He (即 Dan Ghiorso) hopes the company's software will change that, although he has yet to put it to the test during an actual quake. 可知 Dan Ghiorso 希望该公司的软件能够改变他所在区域(即Woodside Fire Protection District)的现状，尽管他还没有在真正的地震中进行测试。即该软件是否在Woodside Fire Protection District有用还有待实践证明，故D项排除；A、B选项在文中均未提及，排除。故答案选C。
深色：已答题 浅色：未答题