The correct answer is: Census Act, 1948.
The Census Act, 1948 is an Act of the Parliament of India to provide for the taking of a census of the population of India at such intervals as may be specified by the Central Government. The Act also provides for the maintenance of a population register and for the publication of the results of the census.
The Right to Information Act, 2005 is an Act of the Parliament of India to provide for setting out the practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of the Government.
The National Statistical Commission Act, 2005 is an Act of the Parliament of India to provide for the establishment of a National Statistical Commission to advise the Central Government on statistical matters and to promote the development of statistics in India.
The Official Secrets Act, 1923 is an Act of the Parliament of India to provide for the protection of certain official documents and information. The Act prohibits the unauthorized communication of official information and the unauthorized possession of official documents.
The Census Act, 1948 is the most relevant Act for the question as it specifically provides for the taking of a census of the population of India. The other Acts are not directly related to the taking of a census.