The correct answer is Raipur.
Raipur is the capital of Chhattisgarh and the most populous district in the state. It has a population of over 3.5 million people. The city is located on the banks of the Mahanadi River and is a major industrial and commercial center. Raipur is also home to a number of educational institutions, including the University of Raipur.
Durg is the second most populous district in Chhattisgarh, with a population of over 2.5 million people. The district is located in the central part of the state and is known for its coal mines. Durg is also home to a number of industrial and commercial centers.
Rajnandgaon is the third most populous district in Chhattisgarh, with a population of over 2 million people. The district is located in the southern part of the state and is known for its agriculture. Rajnandgaon is also home to a number of educational institutions, including the Government Engineering College, Rajnandgaon.
Bilaspur is the fourth most populous district in Chhattisgarh, with a population of over 1.5 million people. The district is located in the northern part of the state and is known for its coal mines. Bilaspur is also home to a number of industrial and commercial centers.