铆钉在一截面上受剪力，称为单剪。

（1）解方程x²-2x-4=0

（2）解方程（x+4）²=5（x+4）

关于氟的抗龋机制，正确的描述是（）

A.降低釉质的溶解性

B.促进釉质脱矿物质的再矿化

C.降低釉质表面自由能

D.干扰细菌代谢

E.以上都是

铆工操作按工序性质可分为几部分？

党的十八大报告指出，全面建成小康社会，实现中 * * 伟大复兴，必须推动社会主义文化大发展大繁荣。某校高二（1）班的同学围绕我国的文化发展问题开展了研究性学习。同学们对《我是歌手》《妈妈咪呀》等综艺节目进行了分析研究，发现2013年我国新开播的综艺节目都是引进国外版权的，同时还有许多电视台准备加入引进的队伍。同学们在讨论中形成了两种观点。

观点一：综艺节目在中国起步较晚，“拿来主义”是一个必经之路。

观点二：盲目跟风引进国外节目，不利于中国电视行业的发展。

选择一种你赞成的观点，运用文化生活相关知识简要说明理由。

For more than two centuries, American’s colleges and universities have been the backbone of the country’s progress. They have educated the technical, managerial, (1) and provided generation after generation of national leaders. Today educators from around the globe are turning to U. S. institutions of higher learning (2) . They are apt to find many reasons for the excellence of American universities, but (3) stand out as watersheds:
Education (4) : In 1862 Congress enacted the Land-Grant College Act, which essentially extended the opportunity of higher education (5) , including such disenfranchised groups as women and minorities. Each state was permitted to sell large tracts of (6) and use the proceeds to endow at least one public college.
(7) : Over the years, the decentralization and diversity of the America’s colleges and universities have promoted competition for students and resources. Competitive pressure first arose (8) . The academy’s impact really grew after World War II, when (9) commissioned by President Roosevelt argued that it was the federal government’s responsibility to (10) for basic research. Instead of being centralized in government laboratories, scientific research (11) in American universities and generated increasing investment. It also gave graduate students research opportunities and helped (12) far and wide, to the benefit of industry, medicine and society as a whole.
(13) : The end of the World War II saw passage of the Servicemen’s Readjustment Act of 1944. The law, which provided for (14) for returning veterans, made an already democratic higher-education system accessible in ways that were (15) in Europe, opening the doors of the best universities to men and women who had (16) of going to college.
(17) : The creation of federal loan guarantees and subsidy programs, as well as outright grants for college students brought (18) to higher education and further helped to democratize access. Since its founding (19) , the Federal Family Education Loan Program has funded more than 74 million student loans worth more than (20) .