The correct answer is Seventh.

• Census 2011 was the 15th National Census of the country since 1872 and the 7th after Independence.
• This census was conducted in two phases which are as follows:
  • House listing :
    • The first phase was conducted between April and September across the country, in 2010 depending on the convenience of different states/UTs.
  • Population enumeration :
    • The second phase began all over the country from February 9, 2011, and continued up to February 28, 2011.
•  Information for National Population Register (NPR) was also collected in the first phase, which will be used to issue a 12-digit unique identification number to all registered Indian residents by the Unique Identification Authority of India (UIDAI).
• The second population enumeration phase was conducted between 9 and 28 February 2011. 

• The first complete census of India was conducted in 1830 by Henry Walter in Dacca (now Dhaka).
• In this census the statistics of the population with sex, broad age group, and the houses with their amenities were collected.
• Second Census was conducted in 1836-37 by Fort St.George according to the government website of Census India.
• In this census, the main emphasis was not only laid on complete coverage but also on the classification of demographic, economic and social characteristic took in the entire continent of British India (except Kashmir).
• The next census will happen in the year 2021.

• Census 2021
  • The Census 2021 will be conducted in 18 languages out of the 22 scheduled languages (under 8th schedule) and English, while Census 2011 was in 16 of the 22 scheduled languages declared at that time.
    • It also will introduce a code directory to streamline the process
  • The option of “Other” under the gender category will be changed to “Third Gender”.
    • There were roughly 5 lakh people under the "other" category in 2011.
  • For the first time in the 140 year history of the census in India, data is proposed to be collected through a mobile app by enumerators and they will receive an additional payment as an incentive.
  • The Census data would be available by the year 2024-25 as the entire process would be conducted digitally and data crunching would be quicker.
  • Data from the Census 2011 is still being released. E.g.: The dataset on migration was published recently.