The correct answer is: b) 2011.
The 2011 Census of India was the 14th national census conducted in India. It was conducted by the Office of the Registrar General and Census Commissioner, India, under the Ministry of Home Affairs. The census was conducted from 9 February to 28 February 2011. The total population of India as per the 2011 census was 1,210,193,422. The population of Arunachal Pradesh as per the 2011 census was 1,387,292.
The 2021 Census of India is the 15th national census conducted in India. It is being conducted by the Office of the Registrar General and Census Commissioner, India, under the Ministry of Home Affairs. The census is being conducted from 1st April to 30th September 2021. The final results of the census are expected to be released in 2023.
The 2023 Census of India is not yet conducted.