Solution:In the Pre-Mauryan period, there were sixteen powerful states known as the sodas-mahajanapadas. The mahajanapadas were larger and more powerful than janapadas, and their rulers exercised greater power and enjoyed more prominence than the rulers of the janapadas.These mahajanapadas were Kasi, Kosala, Anga, Magadha, Vajji, Malla, Chedi/Cheti, Vatsa, Kuru, Panchala, Matsya, Surasena/Shurasena, Assaka, Avanti, Gandhara and Kamboja.. Kalinga was not one of these kingdoms. Smaller or weak kingdoms and the republics were eliminated by the stronger rulers and by the sixth century, only four powerful kingdoms remained.