Which one of the following rivers is NOT the part of Indian Ganga river basin?

1. A

   Punpun river

   (a) Punpun river. This option claims that the Punpun river is part of the Indian Ganga river basin. In reality, the Punpun is a southern tributary of the Ganges originating in Palamu district and joining the Ganges downstream, which makes it part of the Ganga basin.

2. B

   Ajoy river

   (b) Ajoy river. This option claims that the Ajoy river is part of the Indian Ganga river basin. The Ajoy flows through Jharkhand and West Bengal, ultimately draining into the Bhagirathi, a distributary of the Ganges, thus falling within the extended basin.

3. C

   Jalangi river

   (c) Jalangi river. This option claims that the Jalangi river is part of the Indian Ganga river basin. The Jalangi is a distributary of the Padma-Ganges system in West Bengal and is directly associated with the Ganga river network.

4. D

   Jonk river

   (d) Jonk river. This option claims that the Jonk river is part of the Indian Ganga river basin, but this is incorrect. The Jonk river is a notable tributary of the Mahanadi river system, flowing through Chhattisgarh and Odisha, and therefore belongs to the Mahanadi basin rather than the Ganga basin.

Summary. Official key is (d) because the Jonk river is a tributary of the Mahanadi river system and lies entirely outside the Ganga river basin. Options (a), (b), and (c) all name rivers that are directly or indirectly linked to the Ganga river network in India. The Punpun is a direct southern tributary of the Ganges in Bihar. The Ajoy and Jalangi are associated with the lower stretches and distributaries of the Ganga system in West Bengal. Therefore, only the Jonk river fails to belong to the Indian Ganga river basin.