The correct answer is option 3, Kolkata. The headquarters of the Botanical Survey of India is located in Kolkata. The Botanical Survey of India is an organization under the Ministry of Environment, Forests and Climate Change in the Government of India. It is responsible for surveying and documenting the plant resources of India. The headquarters in Kolkata serves as the central administrative office for the organization. Option 1, Lucknow, is incorrect as the headquarters is not located there. Option 2, Darjeeling, is also incorrect as the headquarters is not located in Darjeeling. Option 4, Oottacamund, is also not correct as the headquarters is not in Ooty.