The correct option is A Avanti
Out of 16 Mahajanapadas, four were very powerful. These included Magadha, Vatsa, Avanti and Koshala. These four Mahajanpadas engaged in the struggle for supremacy from 6th Century BC to 4th Century BC. The enmity between Magadha and Avanti rose to its zenith when Udaiyn, the successor and son of Ajatshatru was murdered upon the instigation of the king of Avanti. Finally, the hundred years of enmity between the two ended when the Shishuganga dynasty of Magadha destroyed the Prayota dynasty of Avanti and captured it.