阅读下列材料作答
今大道既隐，天下为家，各亲其亲，各子其子，货力为己，大人世及以为礼。
——〈礼记·礼运篇〉
请回答：
（1）这种“天下为家”的局面是因为谁而开始？
（2）他破坏了禅让制，而采取了什么制度？
（3）我国历史上第一个国家，是什么王朝？ 

下列不属于生态系统的是（  ）

一个最简真分数，分子与分母的和为7，这样的分数的和是（）

短文改错。

    Jim Green teaches our ____ English. He has been in China for more than two year____. He has been to many interesting places in Beijing, and____  he has not yet been to many others ____ parts of China. Last week he goes ____ to Mount Emei in Sichuan Province with his family. Many people like travel ____ by air, but Jim ____ family think that traveling by train is the best. It is much cheap ____ and far more enjoyable than a rushing trip by air. He ____ had a wonderful train ride to Chengdu after ____ they went to Mount Emei by bus.