The correct answer to the question "The Gandhi Sagar reservoir is of the river" is option 1, Chambal. The Gandhi Sagar reservoir is a large water reservoir located on the Chambal River.

Option 2, Narmada, is incorrect as the Narmada River does not have a reservoir called Gandhi Sagar. The Narmada River is a major west-central Indian river known for its scenic beauty and cultural importance.

Option 3, Rihand, is also incorrect as Rihand reservoir is located on the Rihand River, not the Chambal River. The Rihand River is a tributary of the Son River and is situated in the state of Uttar Pradesh in India.

Option 4, Sutlej, is also incorrect as the Gandhi Sagar reservoir is not related to the Sutlej River. The Sutlej River is a transboundary river that flows through India and Pakistan.

So, option 1, Chambal, remains the correct answer as the Gandhi Sagar reservoir is indeed located on the Chambal River.