The correct answer is: B) 2021.
The decennial census of India is a census of the population of India, conducted by the Office of the Registrar General and Census Commissioner, India, under the Ministry of Home Affairs. The census is conducted every ten years, with the most recent census being conducted in 2021. The census provides a detailed profile of the population of India, including its size, distribution, age, sex, religion, language, literacy, and occupation. The data collected by the census is used to plan and implement development programs, and to monitor the progress of development.
Option A is incorrect because the 2011 census was conducted in 2011.
Option C is incorrect because the 2023 census has not yet been conducted.
Option D is incorrect because the census is not conducted annually.