THE 2,298-kiIometer Beijing-Guangzhou High-speed Railway ____ (official) opened to passengers on December 26，2012. It is the world’s longest high-speed rail route. The ____ (design)speed of the track is 350 km^, though speeds during the initial period of operation will be limited to about 300 km/h. The new route cuts the travel time between Beijing and Guangzhoualmost two thirds, from 22 hours to roughly eight hours .On December 1, 2012，not long before the opening of the Beijing-Guangzhou High-speed Railway, the Harbin-Dalian High-speed Railway, ____ first high-speed line ever to cross land that lies frozen for almost half a year, began operations, ____ allows passengers to appreciate the view off the coast from Dalian in the morning, ____ the winter snowscape of frosty Harbin in the afternoon .At present the total __ (long) of high-speed lines in China ___(reach)9,349 km. With four main lines ___ (run) east-west and four north-south, the country’s high-speed train network is the world’s largest. China plans to expand _ high-speed railway network to 50，000 km by 2020, to cover almost all large and medium-sized cities.