The best way of learning a language is using it .The best way of learning English is talking in English as much as possible. Sometimes you'll get your words mixed up ( 混合)and people will not understand you .Sometimes people will say things too quickly and you can't understand them. But if you keep your sense of humor (幽默感),you can always have a good laugh at the mistakes you make(你所犯的错误). Don't be unhappy if people seem to be laughing at your mistakes（错误）. It is better for people to laugh at your mistakes than to be angry with you. because they don't understand what you are saying .The most important thing for learning English is : “Don't be afraid of making mistakes because everyone makes mistakes. ”

2014年5月26日,中共中央政治局召开会议,研究进一步推进新疆社会稳定和长治久安工作。会议认为,要采取特殊措施支持南疆发展,加大以贫困群体为重点的民生改善力度。采取特殊措施支持南疆发展是基于（  ）

①民族区域自治制度的中心工作和核心内容是发展经济　②南疆的发展是加强南疆地区各民族大团结的物质保证　③坚持各民族共同繁荣的原则,体现社会主义的本质要求　④坚持民族平等原则,为民族团结打好坚实的政治基础

某企业接到生产3000台某产品的A，B，C三种部件的订单，每台产品需要这三种部件的数量分别为2，2，1（单位：件）．已知每个工人每天可生产A部件6件，或B部件3件，或C部件2件．该企业计划安排200名工人分成三组分别生产这三种部件，生产B部件的人数与生产A部件的人数成正比，比例系数为K（K为正整数）．

下列关于实验操作步骤的叙述，正确的是