某化学兴趣小组发现铜片在加热的条件下可以与浓硫酸反应，产生气泡并闻到刺激性气味，铜片溶解，溶液呈蓝色，请你参与实验探究．

【查阅资料】SO₂是一种无色，有刺激性气味，有毒的气体．

【提出问题】产生的气体是什么？

20世纪80年代以后，东北三省的工业发展滞缓，原因不正确的是（    ）

一条单线铁路线上有A，B，C，D，E五个车站，它们之间的路程如下图所示（单位：千米）．两列火车从A，E相向对开，A车先开了3分钟，每小时行60千米，E车每小时行50千米，两车在车站上才能停车，互相让道、错车．两车应该安排在哪一个车站会车（相遇），才能使停车等候的时间最短，先到的火车至少要停车多长时间？

    It's a Sunday morning. Mr Su's family are at home. They don't go to work or go to school today. Look, Mr Su is in the study. He is reading a newspaper. Su Hai is in her bedroom. She is cleaning the windows. Where is Su Yang? She is in the bedroom too. She is sweeping the floor. Now their bedroom is very clean. Mrs Su is in the bathroom. She is washing the clothes . Look, what's on the sofa? It's their cat, Mimi. It's sleeping.