如图所示，闭合开关S时，小电灯L₁、L₂都不亮。用一段导线的两端接触a、b两点时，两灯都不亮；接触b、c两点时，两灯也不亮；接触c、d两点时，两灯都亮。对此，下列判断中正确的是（ 　  ）

化简：2x²﹣3x²=____ 

9岁，母亲因病早逝，15岁，父亲中风偏瘫住院，16岁，“背”起爸爸去上学……每天一大早，同宿舍的同学还没有起床，陈春林就必须爬起来赶去医院，照顾父亲起床洗漱、喂饭喝水、搓背按摩……安顿好父亲之后，她才放心赶回去上课，中午、晚上也是如此，广西“最美孝心女孩”、第五届全国道德模范陈春林在贺州高中继续用真情演绎着“带父亲上学”的孝心故事，陈春林的经历告诉我们（    ）

①要担负起自己应承担的责任                      ②不同的角色有不同的责任

③未成年子女都要履行赡养父母的义务      ④要以爱和孝敬来报答父母的养育之恩

    If you want to learn a new language, the very first thing to think about is why. Do you need it for a 1reason, such as your job or your studies?2 perhaps you're interested in the 3 , films or music of a different country and you know how much it will help to have a 4 of the language.

    Most people learn best using a variety of 5, but traditional classes are an ideal（理想的）start for many people. They6an environment where you can practice under the 7 of someone who's good at the language. We all lead 8 lives and learning a language takes 9. You will have more success if you study regularly, so try to develop a 10. It doesn't matter if you haven't got long. Becoming fluent in a language will take years, but learning to get by takes 11.

    Many people start learning a language and soon give up. “I'm too 12, ” they say. Yes, children do learn languages more 13 than adults, but research has shown that you can learn a language at any 14. And learning is good for the health of your brain, too. I've also heard people 15 about the mistakes they make when 16. Well, relax and laugh about your mistakes 17 you're much less likely to make them again.

    Learning a new language is never 18. But with some work and devotion, you'll make progress. And you'll be 19 by the positive reaction of some people when you say just a few words in 20 own language. Good luck!