The correct answer is C. Rajgir.
Krishi Kumbh Mela is a national-level agricultural fair held in India every year. It is organized by the Ministry of Agriculture and Farmers Welfare, Government of India. The fair is held in a different state every year. The 2019 edition of the fair was held in Rajgir, Bihar from 15 to 24 February 2019.
The fair was inaugurated by the Prime Minister of India, Narendra Modi. The fair was attended by over 10 lakh farmers from all over India. The fair showcased the latest agricultural technologies and practices. It also provided a platform for farmers to interact with experts and learn about new ways to improve their agricultural practices.
The fair was a huge success. It helped to promote agricultural development in India and to improve the lives of farmers.
Option A is incorrect because Champaran is a district in Bihar.
Option B is incorrect because Motihari is a city in Bihar.
Option D is incorrect because Gaya is a city in Bihar.
Option E is incorrect because the fair was held in Rajgir, Bihar.