(2007? Weihai) Read the materials and complete the following questions: Materials 1: In July 20061day, the Qinghai-Tibet Railway was opened to traffic, which created countless miracles.

Look at the map. (1) A is the source of the Yangtze River, B is the Qaidam Basin, and C is the Kunlun Mountain. The main ethnic minority living on the Qinghai-Tibet Plateau is Tibetans.

(2)D and E are two provincial capitals on the Qinghai-Tibet Plateau, and the Potala Palace is located in E city.

(3) There are three worldwide engineering problems in the construction of Qinghai-Tibet Railway. The main reasons are high terrain and cold climate.

(4) The trains entering Tibet are fully enclosed, so it is necessary to fill the carriages with oxygen when driving on the plateau, mainly because of the high terrain and thin air.

(5) In recent 30 years, the permafrost in Qinghai-Tibet Plateau is characterized by the shortening of frozen soil duration and the reduction of maximum frozen soil depth. The reason is: global warming.

So the answer is: (1) Yangtze River; Qaidam; Kunlun; Hide; (2)E； (3) the terrain is high and the climate is cold; (4) the terrain is high and the air is thin; (5) Global warming.