Answer:
A.Ural
Step-by-step explanation:
The mountain range that borders Central Asia is the Ural Mountains, which run from north to south and form the eastern boundary of Europe and the western border of Asia. They are considered to be the natural boundary between Europe and Asia, and separate the vast West Siberian Plain of Russia to the east from the lowlands of Kazakhstan to the west. The Ural Mountains stretch for about 2,500 kilometers from the Arctic Ocean in the north to the Ural River and Kazakhstan in the south.
The Caucasus Mountains, on the other hand, are located to the southwest of Russia, while the Syr Dar'ya River is a major river that flows through Central Asia but does not form a mountain range. Therefore, the correct answer is A. Ural, which is the mountain range that forms the eastern border of Central Asia.