Option d is the correct answer. The Chola empire was based in the Kaveri River valley, which runs southeast through Karnataka, Tamil Nadu, and the southern Deccan Plateau to the Bay of Bengal. At its height, the Chola empire controlled not only southern India and Sri Lanka, but also the Maldives and parts of Southeast Asia. The Chola dynasty was one of the Tamil dynasties in southern India and one of the Three Crowned Kings of Tamilakam, along with the Chera and Pandya. The Chola empire was at its peak and achieved imperialism under the Medieval Cholas in the mid-9th century CE.