Unit 1 ?李颖： We are going to ascend the great wall tomorrow morning. So I ’d like to go to bed early and have a good sleep this evening. You know climbing the great wall is not an easy job. ?明天早上我们计划去爬长城，所以我想今晚早点休息，好好睡一觉。你知道爬长城可不是一件简单的事情。?Jack: Great. The Great Wall is very famous and becomes a must for tourist in Beijing. Would you tell me something about it? ?好啊。长城那么有名，是游客来北京必去的景点。你能和我说一说长城么？?李颖： OK. The construction of the great wall took altogether over 2000years.it started in the Zhou dynasty in the 7th century. B.C. And continued until Ming Dynasty in the 15th century A.D. The existing wall was built in the Ming Dynasty. ?好。长城的整个建筑过程持续了总共两千多年，始于公元七世纪的周朝，后来一直延续到公元后十五世纪的明朝。现存的城墙都是明朝修建的。?Jack: The Great Wall is indeed the crystallization of the industry and wisdom of the Chinese people and also a symbol of ancient Chinese culture. Then why the ancient people built the wall? ?长城的确是中国人民勤劳智慧的结晶，同时也是中国古代文化的象征.那么为什么古代人民要修建长城呢？?李颖： It was constructed to guard against the invasion by nomadic tribes from the north. When enemy troops approached, guards on watch would send smoke signals from the beacon-fire towers as an alarm. ?修建长城是为了抵御来自北方游牧民族的入侵。敌军逼近时，放哨的警卫就会在烽火台上发送烟雾信号作为警报。?Jack: How did they manage to do so? Can you be more specific? ?他们怎么发送烟雾信号作为警报呢？你能说的具体点么？?李颖： Those towers on the wall are spaced at equal distances from each other. When guards in a tower saw the signals from its neighbor, they immediately did the same thing .In this way; the signals would be relayed to the...
