中共历史上有许多具有转折意义的会议，其中被称为党的历史上和中国革命史上生死攸关转折点的是（    ）

中华民族在世界冶金史上曾谱写过辉煌的篇章，早在两千多年前的西汉时期就有“曾青得铁则化为铜”的记载，这种方法是现代湿法冶金的先驱．从现代化学的观点理解，这句话的涵义是（　　）

有人通过闻茶的方法就能判断出茶的产地。人们能够闻到茶香的原因是（）

      On weekdays, David gets up at 6:30.He has breakfast at seven and then he goes to school by bus. He gets there at 7:15. He doesn't like to be late. Classes begin at 8:00. He has lunch at twelve at school. He goes home at 5:30 in the afternoon. On weekends, he gets up at about 8:00 and makes breakfast for his family. His parents like him very much.