the world's first underground train system, with the first section opening in 1863. Since then it 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).
翻译： 伦敦地铁是英国的一个快速交通运输系统，服务于大伦敦的大部分地区。地铁系统因其地铁隧道的典型形状也被称为地下管道。伦敦地铁始建于19 世纪中期，是世界上最早的地下铁路系统。它的第一段地铁于1863 年开始运营。自此，伦敦地铁不断延伸，发展成为一个包括12条线路、275个车站、铁轨总长超过250 英里的地铁杰作，其中有45％在地下运行。就路线长度而言，它是世界上第四大地铁系统，也是车站数量最多的地铁系统之一。作为一个走遍伦敦的经济便捷的途径，伦敦地铁一向是每天数百万通勤者以及在节假日游历伦敦的游客的首选。伦敦地铁已成为伦敦的一个国际标志。2013 年伦敦举办了各种各样的活动，庆祝地铁运营150 周年，纪念这一里程碑。
原文：
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。
翻译： 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
原文：
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