The correct option is "Only two" because pairs II (Kamboja — Vipas) and IV (Kosala — Sarayu) are historically accurate, as Kamboja is indeed associated with the Vipas river (identified with the Beas), and Kosala is linked to the Sarayu river. However, pair I (Asmaka — Godavari) is incorrect, as Asmaka is associated with the region near the Godavari's basin but not exclusively with the river. Pair III (Avanti — Mahanadi) is also incorrect, as Avanti is linked to the region around the Narmada river and not the Mahanadi. Understanding these geographical and historical connections is crucial for the UPSC Prelims, where a grasp of ancient Indian geography and its relationship with political or cultural regions is tested.