has grown to an underground masterpiece (杰作) of 12 lines, 275 stations, and over 250 miles of rail track, 45% of which is underground. It is the fourth largest metro system in the world in terms of route miles. It also has one of the largest numbers of stations. As an affordable and easy way to get around London, the Tube remains the first choice for millions of commuters each day, as well as tourists visiting the city on holidays. The Tube has been an international icon for London. The London Underground celebrated its 150 years of operation in 2013, with various events marking the milestone (里程碑).
中国航天业开创于1956年。几十年来，中国航天事业创造了一个又一个奇迹。1970年，中国成功发射了第一颗人造地球卫星，成为世界上第五个独立自主研制和发射人造地球卫星的国家。1992年，中国开始实施载人航天飞行工程（manned spaceflight program）。2003年，中国成功发射了\神舟五号\载人飞船，使中国成为第三个发射载人飞船的国家。2007年发射了\嫦娥一号\，即第一颗绕月球飞行（lunar-orbiting）的人造卫星。2013年，第五艘载人飞船\神舟十号\发射成功，为中国空间站的建设打下了基础。
China's space industry was launched in 1956. Over the past decades, China's space industry has created one miracle after another. In 1970 China launched its first man-made earth satellite, ranking China the fifth country in the world to independently develop and launch man-made earth satellites. In 1992 China began to carry out the manned spaceflight program. In 2003 China launched Shenzhou-5, a manned spaceship. The successful launch made China the
third country to launch manned spaceships. In 2007 Chang'e-1, the first lunar-orbiting man-made satellite, was sent to space. In 2013 Shenzhou-10, the fifth manned spaceship, was launched successfully, laying the foundation for building the Chinese Space Station. Unit 4
作为通过中国游历亚洲的首批欧洲人之一，马可?波罗可能是中国人最熟知的外国商人和航海家。从1271 年到1295 年，他和他的家人游历广泛，遍及欧洲和亚洲。期间，他在中国留居了17 年。他的著作《马可?波罗游记》描述了他游历亚洲的旅程，让欧洲人首次全面领略了包括中国、印度和日本在内的远东地区的情况。从他的文字叙述中，西方人第一次了解到瓷器、煤炭、火药、印刷术、纸币以及丝绸。在15 世纪末和16 世纪欧洲发现与征服的大航海时代，马可?波罗所记录的大量新的地理信息得到了广泛使用。在他去世后的这几个世纪里，马可?波罗获得了他在有生之年未曾获得的赞誉。马可?波罗的故事鼓舞了其他无数的探险者去踏上征程，发现世界。
As one of the first Europeans to travel across Asia through China, Marco Polo is perhaps the most well-known foreign merchant and voyager to the Chinese people. He traveled extensively (广泛地) with his family, journeying from Europe to Asia from 1271 to 1295. He remained in China for 17 of those years. His book The Travels of Marco Polo depicts his journeys throughout Asia, giving Europeans their first comprehensive look into the Far East, including
China, India, and Japan. From his written accounts the Westerners learned of porcelain, coal, gunpowder, printing, paper money, and silk for the first time. The wealth of new geographic information recorded by Polo was widely used in the late 15th and the 16th centuries during the age of the European voyages of discovery and conquest (征服). In the centuries since his death, Marco Polo has received the recognition that failed to come his way during his lifetime. Marco Polo's story has inspired countless other adventurers to set off and see the world.
郑和是中国历史上最著名的航海家（maritime explorer）。公元1405 年，明朝的统治者为了稳固边防（border defense）和开展海上贸易，派郑和下西洋（the Western Seas）。在此后的28 年里，郑和带领船队七下西洋，前后出海的人员有10 多万人，访问了30 多个国家和地区。船队纵横南亚、西亚，一直到非洲大陆。郑和下西洋是世界航海（navigation）史上的壮举，它展现了郑和卓越的航海和组织才能，同时展现了明朝的国力和国威（national strength and prestige），加强了明朝和海外各国之间的关系。
Zheng He was the most famous maritime explorer in Chinese history. In 1405 AD, the ruler of the Ming Dynasty sent Zheng He on a voyage to the Western Seas in order to strengthen border defense and develop trade by sea. In the following 28 years, Zheng He led his fleet, made seven voyages to the Western Seas with over 100,000 crew members in total, and visited more than 30 countries and regions. The fleet traveled far into South Asia and West Asia,
and made all the way to the continent of Africa. Zheng He's voyages to the Western Seas were a great feat in the world's navigation history. It showed Zheng He's outstanding navigation and organization talents; meanwhile, it exhibited the national strength and prestige of the Ming Dynasty, and strengthened the relationships between the Ming Dynasty and the overseas countries. Unit 5
有关古代奥林匹克运动会的最早文字记载可追溯至公元前776年。古代奥运会每4年举办一次，在8月6日与9月19日之间的一个纪念宙斯的宗教节日期间举行。第一届现代奥运会于1896年在希腊雅典举办。奥运会的标志由五个大小相同的套环组成，代表着五大洲的联合和来自世界各地运动员的大聚会。奥运会真正腾飞、成为一项国际体育盛会是在1924年之后，即第8届奥运会在巴黎举办之后。这一年，来自44个国家约3,000名运动员同场竞技，并且第一次在奥运会上增加了闭幕式这一仪式。同年，冬季奥运会首次亮相，比赛项目包括花样滑冰、冰球、雪橇和冬季两项运动。80年后，2004年夏季奥运会在相隔一个多世纪后再次在雅典举办，来自201个国家的近11,000名运动员展开竞技，创下参赛国数量之最。
The first written records of the ancient Olympic Games date to 776 BC. The ancient Olympics were held every four years between August 6 and September 19 during a religious festival honoring Zeus (宙斯). The first modern Olympics were held in Athens, Greece, in 1896. The Olympic symbol