一块24公顷的地，一台拖拉机3小时耕了它的18，照这样计算，耕完这块地需要几小时

小倩同学发现妈妈将一种商品名为“除垢净”的液体，倒在白色瓷质洗脸盆的水垢上，一会儿发现有大量的气泡产生，白色瓷质洗脸盆的水垢被除去．

【提出猜想】联想水垢的主要成分是碳酸钙．小倩猜想“除垢净”的成分中可能有酸．

【设计方案进行实验】小倩找来两类不同的物质进行实验，并得出了下表结论．请你参与，并完成实验报告．

（1）若在稀HCl和稀H₂SO₄两种酸中，选择一种酸用作“除垢净”的有效成分，你认为应该选择的酸是（选填名称）______；

（2）结合上面对“除垢净”的了解，在使用“除垢净”时应注意______．

乳腺癌改良根治术后进行肩活动功能康复，错误的是（）。

A.手术切口引流条没有撤除前外展限制于45°以内

B.等长收缩练习

C.第1～2天开始肩的被动活动

D.使术侧肩部置于功能位

E.内旋、外旋应受限制

精溶剂油中碘值为（）。

A.大于0.2g/100g

B.小于0.2g/100g

C.等于0.2g/100g

D.小于等于0.2g/100g

A hundred years ago it was assumed and scientifically" proved" by economists that the laws of society made it necessary to have a vast army of poor and jobless people in order to keep the economy going. (46) Today, hardly anybody would dare to voice this principle. It is generally accepted that nobody should be excluded from the wealth of the nation, either by the laws of nature or by those of society. The opinions, which were current a hundred years ago, that the poor owed their conditions to their ignorance, lack of responsibility, are outdated. In all Western industrialized countries, a system of insurance has been introduced which guarantees everyone a minimum of subsistence (生活维持费) in case of unemployment, sickness and old age. I would go one step further and argue that, even if these conditions are not present, everyone has the right to receive the means to subsist(维持生活), in other words, he can claim this subsistence minimum without having to have any" reason". (47) I would suggest, however, that it should be limited to a definite period of time. let’s say two years, so as to avoid the encouraging of an abnormal attitude which refuses any kind of social obligation.

This may sound like a fantastic proposal, but so, I think our insurance system would have sounded to people a hundred years ago. The main objection to such a scheme would be that if each person were entitled to receive minimum support, people would not work. (48) This assumption rests on the fallacy of the inherent laziness in human nature ; actually, aside from abnormally lazy people, there would be very few who would not want to earn more than the minimum, and who would prefer to do nothing rather than work.

(49)However, the suspicions against a system of guaranteed subsistence minimum are not groundless from the standpoint of those who want to use ownership of capital for the purpose of forcing others to accept the work conditions they offer. If nobody were forced to accept work in order not to starve, work would have to be sufficiently interesting and attractive to induce one to accept it. (50) Freedom of contract is possible only if both parties are free to accept and reject it ; in the present capitalist system this is not the case.

But such a system would not only be the beginning of real freedom of contract between employers and employees; its principal advantage would be the improvement of freedom in interpersonal relationships in every sphere of daily life.

(47) I would suggest, however, that it should be limited to a definite period of time. let’s say two years, so as to avoid the encouraging of an abnormal attitude which refuses any kind of social obligation.

[Split/Mixed]选项表示（InnerLayer2）层带有平面层属性，可以用[PlaneArea]（平面层区域）工具在这一板层中绘制平面层覆铜。