The correct answer is - D. Ural.
The Ural mountain range is the separating line between Europe and Asia. Geographically speaking it is one continent, Eurasia, not two, but the separation has occurred due to other things. The Ural Mountain Range had been a border between Europe and Asia for millenniums, and that was based not on geography, but on culture, language, religion, lifestyle, race... The division arose because the people west of Ural, and the people east of Ural were different in most things, while the people on the west were white skinned, had languages from the Indo-European branch, were mostly living in villages, towns, and cities, the people from the east were darker skinned, had almond like eyes, were nomads that roamed over vast areas, had languages from different linguistic branch...