Pair 1 is correct: Asmaka (or Assaka) was the southernmost Mahajanapada, located in the Deccan region on the banks of the Godavari river. Pair 2 is incorrect: Kamboja was located in the extreme north-west (modern-day Afghanistan and Kashmir). The Vipas (Beas) river flows through Punjab, which is geographically distinct and east of the Kamboja region. Pair 3 is incorrect: Avanti was in western Madhya Pradesh (Malwa region). The main rivers flowing through it were the Kshipra and Vetravati, not the Mahanadi (which flows through Odisha and Chhattisgarh). Pair 4 is correct: Kosala was a Mahajanapada in present-day eastern Uttar Pradesh. Its capital, Ayodhya, is situated on the banks of the Sarayu river.