The correct answer is Raipur.
Raipur is the capital of Chhattisgarh and the largest city in the state. It is a major railway junction and is well-connected to other major cities in India. The city has a population of over 1.5 million people.
Bilaspur is the second largest city in Chhattisgarh and is also a major railway junction. The city is located in the northern part of the state and has a population of over 1 million people.
Durg is a city in the central part of Chhattisgarh and is a major industrial center. The city has a population of over 600,000 people.
Korba is a city in the eastern part of Chhattisgarh and is a major coal mining center. The city has a population of over 300,000 people.