Plastics are materials which are softened by heat and set into lasting form when shaped in a mold. Some are natural; some are semi-synthetic , the result of chemical action on natural substance; some are synthetic, built up from the constituents of oil or coal. All are based on the chemistry of carbon, with its capacity for forming chains. The molecules that compose them link together in the setting or curing process to form chains , which give plastics their flexible strength. Some plastics retain their ability to be softened and reshaped; like wax, they are thermoplastic. Others set permanently in the shapes they are given by heat and pressure; like eggs, they are thermosetting. From industrial beginnings in the nineteenth century, plastics have struggled through a hundred and twenty years of glory, failure, disrepute and suspicion on the slow road to public acceptance. Now, at last, one can positively say that plastics are appreciated and enjoyed for what they are; that they make modern life richer, more comfortable and convenient, and also more fun. Plastics are warm materials, sympathetic to the human touch, and their transformation into things that come into contact with human beings is entirely appropriate. The fact that there are plastic antiques comes as a shock to most people. How can a material that seems so essentially twentieth century, and one that is so much associated with cheap, disposable products, has a history at all? It is a young technology, and a great part of the fun of collecting plastics is that beautiful pieces of historical interest can still be found very cheaply. 21. The word sympathetic in Paragraph 2 most probably means_______. A. harmful B. agreeable C. pitiful D. sorry 22. It can be concluded from this passage that_______. A. plastics are synthetic materials B. plastics won public acceptance 120 years agoC. plastics are very harmful in modern lifeD. plastics are cheap as antiques 23. Which of the following is essential to create any type of plastics? A. Carbon. B. Eggs. C. Oil. D. Coal. 24. Plastics that harden into permanent shapes are called_______. A. chained B. thermoplastic C. synthetic D. thermosetting 25. Which of the following is the best title for the passage? A. The Importance of Plastics in the Nineteenth Century. B. Why People Are Suspicious of Plastics. C. The Development of Plastics as a Modern Material. D. How Plastics Are Manufactured. 21. B 22. D 23. A 24. D 25. C
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2014人教新目标英语七下unit 3《How do you get to school》section b导学案
2014人教新目标英语七下unit 4 《Don’t eat in class》(第1课时)学案
2014人教新目标英语七下unit 3《How do you get to school》教案4
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2014人教新目标英语七下unit 4 《Don’t eat in class》(第3课时)学案
2014人教新目标英语七下unit 2《What time do you go to school》教案
2014人教新目标英语七下unit 4《Don’t eat in class》period 1教案
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2014人教新目标英语七下unit 3《How do you get to school》(第4课时)section b 1a-1e导学案
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2014人教新目标英语七下unit 4《Don’t eat in class》period 4教案
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2014人教新目标英语七下unit 4 《Don’t eat in class》(第4课时)学案
2014人教新目标英语七下unit 3《How do you get to school》教案5
2014人教新目标英语七下unit 3《How do you get to school》(第3课时)section a grammar focus-3c导学案
2014人教新目标英语七下unit 3《How do you get to school》(第1课时)section a 1a-1c导学案
2014人教新目标英语七下unit 3《How do you get to school》section a导学案
2014人教新目标英语七下unit 2《What time do you go to school》学案4
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2014人教新目标英语七下unit 3《How do you get to school》单元练习题4
2014人教新目标英语七下unit 2《What time do you go to school》单元练习题2
2014人教新目标英语七下unit 4《Don’t eat in class》period 3教案
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2014人教新目标英语七下unit 2《What time do you go to school》(第4课时)学案
2014人教新目标英语七下unit 2《What time do you go to school》单元练习题1
2014人教新目标英语七下unit 3《How do you get to school》单元练习题2
2014人教新目标英语七下unit 2《What time do you go to school》习题精选4
2014人教新目标英语七下unit 4《Don’t eat in class》period 2教案