根据短文内容，选择最佳答案。
It is well-known that it will take travelers only 48 hours by train to go from Beijing to Lhasa， the capital of west China's Tibet on July 1 this year. Travelers can enjoy the beautiful views during the 48 hour train ride.
The new railway line will be controlled by the Beijing' s West Railway Station from July 1， 2006. The most important part of the line， the Qinghai-Tibet Railway， has been completed.
The Qinghai-Tibet part of the railway is the world's highest railway. About 960 kilometers of the train tracks are 4，000 meters above sea level. The highest parts reach 5，072 meters.
The railway is the world' s longest plateau railroad which is 1，956 kilometers long， from Qinghai's capital Xining to Lhasa in Tibet. The Golmud-Lhasa part is 1，142 kilometers long and goes across the Kunlun and Tanggula mountain ranges.
The trains running on the Qinghai-Tibet Railway have very good conditions. If the passengers feel hard to breathe， they will be provided with oxygen masks， because all of the trains have oxygen supplying equipments.
