The correct answer is: c) Registrar General of India
The Registrar General of India (RGI) is the head of the Office of the Registrar General and Census Commissioner, India, which is responsible for conducting the decennial census of India. The RGI is also responsible for maintaining the civil registration system in India.
The Directorate of Census Operations (DCO) is a subordinate office of the RGI, which is responsible for conducting the census in each state and union territory of India. The DCO is headed by a Director of Census Operations, who is appointed by the RGI.
The National Sample Survey Office (NSSO) is a statistical agency of the Government of India, which is responsible for conducting sample surveys in India. The NSSO is not responsible for conducting the census.
The State Government is not responsible for conducting the census. The census is a national exercise, and is conducted by the central government. The State Government may provide some assistance to the RGI in conducting the census, but it is not the primary responsibility of the State Government.