According to the news, the world’s highest railway climbs to more than ______ ab

The Chinese authorities have announced the completion of what they say is the world’s highest railway, connecting Tibet with the rest of China. Beijing has planned the railway since the 1950s, but construction was delayed by high costs and technical obstacles. With more, Daniel Griffiths reports from Beijing:
     The new railway climbs more than 5,000 meters above sea level, running through mountain passes and over Tibet’s snow-covered plateau. It’s a major feat of engineering, crossing some of the most inhospitable terrain in China. Workers have to bore tunnels through ice, and construction crews regularly use bottled oxygen to help them breathe at such heights. The line is due to start operating next year. Passengers will travel in special trains that are sealed like aircraft to protect them from altitude sickness.