借助年代尺我们可以清晰梳理历史发展脉络，认识某一历史时期的时代特征。仔细阅读年代尺，下列对①②③④时代特征的描述，正确的是（    ）

①统一国家的建立

②经济重心南移与民族关系发展

③繁荣、开放与革新

④多民族国家的巩固与危机

照样子把句子写具体。

例如罐子里竟装满了水。 罐子里竟装满了（清澈新鲜的）水

音乐吸引着观众。

____音乐吸引着____观众。

去年1件甲商品可以兑换10件乙商品，1件乙商品可以兑换2件丙商品。假如今年生产甲商品的部门劳动生产率提高了25%。不考虑其他因素，则下列判断正确的有（  ）

①今年1件甲商品可以兑换25件丙商品②今年1件甲商品可以兑换16件丙商品③今年1件甲商品可以兑换12.5件乙商品④今年1件甲商品可以兑换8件乙商品

阅读材料，完成任务。

    My uncle Jack is an interesting man. When he speaks, his mustache（胡子） always dances. It is so funny. He wears glasses and a funny hat.

    I don't like my boss（老板） at all. He is heavy with two small eyes. I think his glasses are too small for him.

— Look, the salesman（商人） is coming.

— Which one?

— The one with short black hair. He always takes his umbrella(雨伞) and suitcase(旅行箱). And his tie is very ugly.

— What are you doing, Lucy? Look at your pants. They are so dirty!

— I am doing some cleaning. Don't come here, Jane. Your beautiful skirt will be dirty.