The correct answer is option C: Bastar forest circle.
Bastar forest circle is the largest forest circle in Chhattisgarh, with a total area of 13,200 square kilometers. It is located in the southern part of the state, and is home to a variety of forests, including sal, teak, and bamboo forests. The circle is also home to a number of wildlife sanctuaries, including the Indravati National Park and the Kanha National Park.
The other options are incorrect because they are not the largest forest circles in Chhattisgarh. Bilaspur forest circle has an area of 8,000 square kilometers, Sarguja forest circle has an area of 6,000 square kilometers, and Raipur forest circle has an area of 4,000 square kilometers.