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汽车及拖拉机的齿轮要求表面具有高硬度、高耐磨性、心部有良好的强韧性，应选用（ ）
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65，65Mn，60Si2Mn、50CrV属于（ ），其热处理特点是（ ）
制造轴、齿轮等零件所用的调质钢，其碳的质量分数是（），为了提高淬透性应加入合金元素（）。
请选择下列零件材料：磨床主轴（ ），板弹簧（），滚珠（），汽车变速齿轮（）。（在以下选项中选出）A、Cr12B、1Cr18Ni9TiC、40CrD、20CrMnTi E、GCr15F、60Si2Mn
Read the passage and decide which of the choices would best complete the passage if inserted in the corresponding blanks.On my arrival in America, the one thing I noticed more than anything else was the 1 _1______ amount of advertising that went on—on the radio, on television, on billboards and signposts, and in magazines. In the last three years, I have become accustomed to this fact in American life, for I believe that it is a creative and necessary part of an industrial 22 ________ . I, too, want to improve my lifestyle and to buy better products, so I 3 3________ to advertising to show me how to do it.Deciding what to believe in advertising, however, isn’t easy. It seems to me that a person must 4 _4_______ things with a lot of care. As a consumer, I want to get the best for my money, so I really have to understand the techniques of advertising. Otherwise, manufacturers will be able to sell me anything, no matter what its quality may be.More and more people are becoming 5 ___5______ , like me, of the ways in which advertising can affect them. The creative aspects of commercials, for instance, often cover up defects or problems in products. I have learned this well, since I have made purchases and lost money because the 6 ___6______ were of poor quality.The future of advertising will most likely involve a much greater 7 ____7______ of public participation. I intend to become involved in consumer groups that want to 8 __8________ people from misleading advertising. But I also want to see Americans keep their high 9 __9__________ of living in the process. In the future, if consumers like me really care about the quality of something as well as the quantity, 10 __10_________ advertisers will begin to care more about what they are trying to sell.
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