设a、b为非零实数，则x=a|a|+|b|b+|ab|ab的所有值组成的集合为_

（8分）（1）小方用右图所示装置对二氧化碳的灭火实验进行研究，观察到的现象是______，实验的结论是_______。

（2）【提出问题】二氧化碳能否支持燃烧？

【猜想假设】镁能在二氧化碳中燃烧。

【查阅资料】①氧化镁、氢氧化镁均是白色难溶于水的固体。  

②MgO+2HCl= MgCl₂+H₂O 、

③MgCl₂+2NaOH=Mg(OH)₂↓+2NaCl 。

【实验探究】

①右图中镁带剧烈燃烧，冒白烟，有黑色固体生成，并放出大量的热。

②为检验生成物的成分，做如下实验。

实验步骤		实验现象	实验结论和化学方程式
向广口瓶中加入过量盐酸，充分反应后过滤，在滤纸上留有黑色固体。	I、将黑色固体收集、洗涤、干燥后，点燃，在火焰上方罩一个蘸有澄清石灰水的烧杯。	黑色固体燃烧，烧杯内壁出现白色浑浊。	黑色固体是______；反应的化学方程式是______。
	II、取少量滤液于试管中，逐滴加入氢氧化钠溶液。	开始_______，后有白色沉淀产生。	白烟的成分是______。

③为了回收II中的白色沉淀，证明沉淀完全的实验方法是______（要求写出步骤、试剂、现象和结论）。

【反思提高】实验室中由某些活泼金属引起的着火，不能用二氧化碳灭火，应用细沙灭火。

Beyond the Factory: Child Labor in the Cities

At the beginning of the nineteenth century, factory owners faced few restrictions on the way they employed their children workers, who were between the age of 7 and 12. Gradually laws came into being.

The first child-labor laws were passed at the state level in America and usually focused on both required education and a minimum age for employment. And added rules limited the length of the workday for children. Pennsylvania, for example, limited the workday to 10 hours for children under 12. However, government officials cared little whether businesses followed the law. In fact one group of children was left entirely unprotected by labor laws -- the children of immigrant families.

By the beginning of the twentieth century, piecework appeared, for which people were paid by the piece. Significant numbers of women sewed baby dresses or men's neckties and made the artificial flowers used to decorate hats. Piecework turned homes into factories that were free from the law, and countless children worked long hours alongside their mothers and old sisters.

Manufactures exploited the system shamelessly and paid the lowest wages they could. Embroidering (刺绣) a silk dress, which was a 10-day job, might generate a five-dollar payment. In the case of "willowing", workers needed to add more strands to ostrich feathers used on hats to make them longer and more graceful. The first willowers were paid 15 cents per inch, but a few months later, the pay was reduced to 13 cents. Within three years, willowers were earning only three cents per inch.

In order to survive under these circumstances, pieceworkers had even their youngest children help them. In one Italian neighborhood, a three-year-old girl helped her mother sew clothes. In another case, a child of eight who had lived in New York for three years had never been to school at all and could speak almost no English. Slowly child labor laws brought these abuses to an end.

31. The first child-labor laws required ______.

A. workplace safety and conditions

B. minimum payment and age

C. education and working time

D. minimum payment and schooling

32. Manufactures who hired women to do piecework ______.

A. were kind and concerned employers

B. were sometimes called "willowers"

C. usually paid the lowest salary

D. forced children to turn home into factories

33. "Willowing" was a kind of ______.

A. handwork activity           B. workplace

C. payment requirement              D. workers

34. By raising the example of the three-year-old girl's experience in the last paragraph, the author intended to ______.

A. show how poor the situations were for children workers

B. blame those adult pieceworkers for allowing children to work

C. attract attention to protect young children

D. emphasize the importance of educating young children

35. Which of the following sentences best summarizes the passage?

A. The first child-labor laws were limited due to working at the state level.

B. Early child-labor laws offered no protection to children who worked at home.

C. Some immigrant children did not learn English because of their piecework.

D. Child-labor laws should have come into being before children became workers.

道路石油沥青及建筑石油沥青的牌号是按其（）划分的。

A．针人度的平均值

B．软化点平均值

C．延度平均值

D．沥青中油分含量

筛号数越小，粉末越细。

干式电抗器竣工（预）验收标准要求如使用金属围栏则应留有防止产生感应电流的间隙；电抗器中心与周围金属围栏及其他导电体的最小距离不得低于电抗器外径的（）倍。

A.1.1

B.1.2

C.1.3

D.1.5