Correct Option (b):
The correct descending order of the given rivers by their lengths is Godavari-Narmada-Mahanadi-Tapi.
The approximate lengths are:
- Godavari: 1,465 km
- Narmada: 1,312 km
- Mahanadi: 858 km
- Tapi: 724 km
Godavari is the longest peninsular river, originating in the Western Ghats of Maharashtra and flowing eastward into the Bay of Bengal. Narmada and Tapi are significant west-flowing rivers. Narmada originates from the Amarkantak plateau in Madhya Pradesh, while Tapi originates from the Satpura range in Madhya Pradesh. Mahanadi originates from the highlands of Chhattisgarh and flows eastward through Odisha into the Bay of Bengal.
Incorrect Options:
Option (a) Godavari-Mahanadi-Narmada-Tapi is incorrect because Mahanadi (858 km) is shorter than Narmada (1,312 km).
Option (c) Narmada-Godavari-Tapi-Mahanadi is incorrect as Narmada (1,312 km) is shorter than Godavari (1,465 km).
Option (d) Narmada-Tapi-Godavari-Mahanadi is incorrect because both Narmada (1,312 km) and Tapi (724 km) are shorter than Godavari (1,465 km).