The correct answer is: C. Gandak
The Gandak Multipurpose Project is a major irrigation and flood control project on the Gandak River in India. It is located in the states of Bihar and Uttar Pradesh. The project was started in 1954 and completed in 1969. It is one of the largest irrigation projects in India.
The project includes a dam, a barrage, and a canal system. The dam is located on the Gandak River in Bihar. The barrage is located on the Gandak River in Uttar Pradesh. The canal system irrigates about 1.2 million hectares of land in Bihar and Uttar Pradesh.
The project also provides flood control for the cities of Patna and Bhagalpur in Bihar. The project has been a major success in terms of irrigation and flood control. It has also had a positive impact on the economy of the region.
The other options are incorrect because they are not multi-purpose projects. The Son River is a tributary of the Ganges River. The Kosi River is a tributary of the Ganges River. The Damodar River is a tributary of the Hooghly River.