完形填空．

　　Located in Shaanxi Province, Xi'an is an important ___1___ of science and technology, culture, education, trade and finance as ___2___ as modern processing（加工）base. ___3___ a population of more than 7 million, Xi'an takes ___4___ an area of 10,108 square kilometers. ___5___ Chang' an in Chinese history, Xi'an was once the capital of 13 dynasties and ____6__ a similar honor as other famous historical cities in the world ___7___ Rome and Athens.

　　The ___8___ Silk Road started there 2,100 years ago, and ___9__ the city into a trade center that connected China with ___10___ countries.

　　The splendid history has blessed the city with numerous valuable relics ___11___ the Qin Terracotta Warriors and Horses and the ancient city walls from the Ming Dynasty.

　　Together with gorgeous natural scenery, those historic sites ___12__ a powerful boost（促进）to the tourism Industry in Xi'an, which ___13___ an important part in the local economy.

　　The city has 56 hotels rated in the tourist-star system which ___14___ foreigners and 174 travel agencies open today.

　　Besides tourism, the time-honoured city has also made ___15___ progress in terms of local economy, ___16___ research and city construction advancement in the past 50 years.

　　With a (n) ___17___ of 13 percent in the gross domestic product (CDP) for 10 continuous years, Xi'an ___18___ a comprehensive industrial system of its own.

　　There are now 43 colleges and more than 660 scientific institutions in Xi'an. Each year it turns ___19___ about 3,000 research achievements or patents（专利）. The city's comprehensive technological power ranks ___20__ in China, next to Beijing and Shanghai.