The correct answer is: b) 10 years.
The Census in India is conducted every 10 years. The first census was conducted in 1872, and the most recent census was conducted in 2011. The census is used to collect data on the population of India, including age, sex, religion, language, and literacy. The data collected by the census is used to plan for the development of India and to ensure that all citizens have access to essential services.
Option a) is incorrect because the census is not conducted every 5 years. The census is conducted every 10 years.
Option c) is incorrect because the census is not conducted every 15 years. The census is conducted every 10 years.
Option d) is incorrect because the census is not conducted every 20 years. The census is conducted every 10 years.