The correct answer is (b), 1982.
The Central Ganga Authority (CGA) was constituted by the Government of India in 1982 to coordinate and monitor the implementation of the Ganga Action Plan (GAP). The GAP was a major initiative launched by the Government of India in 1985 to clean up the Ganga River. The CGA is headed by the Prime Minister of India and has representatives from the Central Government, State Governments, and other stakeholders. The CGA has been instrumental in the implementation of the GAP and has made significant progress in cleaning up the Ganga River.
Option (a), 1975, is incorrect because the CGA was not constituted in that year. The CGA was constituted in 1982.
Option (c), 1985, is incorrect because the GAP was launched in that year, not the CGA. The CGA was constituted in 1982.
Option (d), 1995, is incorrect because the CGA has been in existence since 1982.