Which one of the following mountains separates Black Sea and Caspian Sea?

The Caucasus Mountains are a major mountain system located between the Black Sea and the Caspian Sea. This range stretches across the Caucasus region, encompassing parts of Russia, Georgia, Azerbaijan, and Armenia [4]. It is traditionally considered a natural boundary between Europe and Asia. In contrast, the Ural Mountains are old fold mountains located in Russia that separate Europe from Asia but are situated much further north and east [1]. The Carpathian Mountains are located in Central and Eastern Europe, forming an arc across countries like Romania and Ukraine, while the Balkan Mountains run through the Balkan Peninsula, primarily in Bulgaria. The Caucasus region is noted for its high biodiversity and endemic species due to its unique geographical position between the two seas [4]. Geologically, while the Urals were formed during the Carboniferous to Permian periods [3], the Caucasus are younger mountains formed by the collision of the Arabian and Eurasian plates.

Sources

1. [4] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 10: Types of Mountains > Hercynian Mountains > p. 132
2. [1] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 4: BIODIVERSITY > europe and central Asia > p. 7
3. [3] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 10: Types of Mountains > 1) Very Old Fold Mountains > p. 135