B. develop a passion for leaning C. learn about the adult community D. get away from a confusing world
45. What could be the best title for the passage？（ ） A. The Magic of Reading B. The Pleasure of Reading C. Growing Up with Reading D. Reading Makes a Full Man
C
How does an ecosystem（生态系统）work？What makes the populations of different species the way they are？Why are there so many flies and so few wolves？To find an answer, scientists have built mathematical models of food webs, noting who eats whom and how much each one eats.
With such models，scientists have found out some key principles operating in food webs. Most food webs，for instance，consist of many weak links rather than a few strong ones. When a predator（掠食动物）always eats huge numbers of a single prey（猎物），the two species are strongly linked；when a predator lives on various species，they are weakly linked. Food webs may be dominated by many weak links because that arrangement is more stable over the long term. If a predator can eat several species，it can survive the extinction（灭绝）of one of them. And if a predator can move on to another species that is easier to find when a prey species becomes rare，the switch allows the original prey to recover. The weak links may thus keep species from driving one another to extinction.
Mathematical models have also revealed that food webs may be unstable，where small changes of top predators can lead to big effects throughout entire ecosystems. In the 1960s，scientists proposed that predators at the top of a food web had a surprising amount of control over the size of populations of other species---including species they did not directly attack.
And unplanned human activities have proved the idea of top-down control by top predators to be true. In the ocean，we fished for top predators such as cod on an industrial scale，while on land，we killed off large predators such as wolves. These actions have greatly affected the ecological balance.
Scientists have built an early-warning system based on mathematical models. Ideally，the system would tell us when to adapt human activities that are pushing an ecosystem toward a breakdown or would even allow us to pull an ecosystem back from the borderline. Prevention is key，scientists says because once ecosystems pass their
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tipping point（临界点），it is remarkably difficult for them to return.
46. What have scientists discovered with the help of mathematical models of food webs？ A. The living habits of species in food webs. B. The rules governing food webs of the ecosystems. C. The approaches to studying the species in the ecosystems. D. The differences between weak and strong links in food webs. 47. A strong link is found between two species when a predator______. A. has a wide food choice B. can easily find new prey C. sticks to one prey species D. can quickly move to another place
48. What will happen if the populations of top predators in a food web greatly decline？ A. The prey species they directly attack will die out.
B. The species they indirectly attack will turn into top predators. C. The living environment of other species will remain unchanged. D. The populations of other species will experience unexpected changes. 49. What conclusion can be drawn from the examples in Paragraph 4？ A. Uncontrolled human activities greatly upset ecosystems. B. Rapid economic development threatens animal habitats. C. Species of commercial value dominate other species. D. Industrial activities help keep food webs stable.
50. How does an early-warning system help us maintain the ecological balance？ A. By getting illegal practices under control. B. By stopping us from killing large predators.
C. By bringing the broken-down ecosystems back to normal. D. By signaling the urgent need for taking preventive action.
D
Would you BET on the future of this man？He is 53 years old. Most of his adult life has been a losing struggle against debt and misfortune. A war injury has made his left hand stop functioning，and he has often been in prison.
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Driven by heaven-knows-what motives，he determines to write a book.
The book turns out to be one that has appealed to the world for more than 350 years. That former prisoner was Cervantes, and the book was Don Quixote（《堂吉诃德》）. And the story poses an interesting question: why do some people discover new vitality and creativity to the end of their days，while others go to seed long before？
We've all known people who run out of steam before they reach life's halfway mark. I'm not talking about those who fail to get to the top. We can't all get there. I'm talking about people who have stopped learning on growing because they have adopted the fixed attitudes and opinions that all too often come with passing years.
Most of us, in fact, progressively narrow the variety of our lives. We succeed in our field of specialization and then become trapped in it. Nothing surprises us. We lose our sense of wonder. But，if we are willing to lean，the opportunities are everywhere.
The things we learn in maturity seldom involve information and skills. We learn to bear with the things we can't change. We learn to avoid self-pity. We learn that however much we try to please，some people are never going to love us-an idea that troubles at first but is eventually relaxing.
With high motivation and enthusiasm，we can keep on learning. Then we will know how important it is to have meaning in our life. However, we can achieve meaning only if we have made a commitment to something larger than our own little egos（自我）, whether to loved ones, to fellow humans, to work, or to some moral concept.
Many of us equate（视…等同于）“commitment” with such “caring” occupations as teaching and nursing. But doing any ordinary job as well as one can is in itself an admirable commitment. People who work toward such excellence—whether they are driving a truck, or running a store-make the world better just by being the kind of people they are. They've learned life's most valuable lesson.
51. The passage starts with the story of Cervantes to show that_________. A. loss of freedom stimulates one's creativity B. age is not a barrier to achieving one's goal C. misery inspires a man to fight against his fate D. disability cannot stop a man's pursuit of success
52. What does the underlined part in Paragraph 3 probably mean？ A. End one's struggle for liberty. B. Waste one's energy taking risks. C. Miss the opportunity to succeed.
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D. Lose the interest to continue learning. 53. What could be inferred from Paragraph 4？ A. Those who dare to try often get themselves trapped. B. Those who tend to think back can hardly go ahead. C. Opportunity favors those with a curious mind. D. Opportunity awaits those with a cautious mind. 54. What does the author intend to tell us in Paragraph 5？ A. A tough man can tolerate suffering. B. A wise man can live without self-pity. C. A man should try to satisfy people around him. D. A man should learn suitable ways to deal with life. 55. What is the author's purpose in writing the passage？ A. To provide guidance on leading a meaningful adult life. B. To stress the need of shouldering responsibilities at work. C. To state the importance of generating motivation for learning. D. To suggest a way of pursuing excellence in our lifelong career.
2019年普通高等学校招生全国统一考试（天津卷）英语 笔试 第Ⅱ卷
注意事项：
1. 用黑色墨水的钢笔或签字笔将答案写在答题卡上。 2. 本卷共6小题，共35分。 第三部分：写作
第一节：阅读表达（共5小题；每小题2分，满分10分） 阅读短文，按照题目要求用英语回答问题。
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