Answer : 3. "Ghaghra"
Explanation :

1. Ghaghra River is the largest tributary of the River Ganga.

2. It flows through Uttar Pradesh and Bihar. The origin area of the Ghaghra River is in the Himalayan Mountains of the Pithoragarh district of Uttarakhand.

3. Ghaghra River joins Ganga River in Gorakhpur district of Uttar Pradesh.

4. Sabarmati river flows in Gujarat.

5. Mahi river flows in Rajasthan and Gujarat.

6. The Bhima River flows in Maharashtra.