Godavari is the longest among them, followed by Narmada, Mahanadi, and Tapi.
A. Godavari-Mahanadi-Narmada-Tapi – Incorrect. Narmada is longer than Mahanadi.
B. Godavari-Narmada-Mahanadi-Tapi – Correct. Right descending order.
C. Narmada-Godavari-Tapi-Mahanadi – Incorrect. Godavari is longer than Narmada.
D. Narmada-Tapi-Godavari-Mahanadi – Incorrect. Random order.