Option (D) is correct because the provided text states that the Government of India passed the Wild Life (Protection) Act, 1972, 'To protect, preserve and propagate the variety of species within natural boundaries', under which national parks and sanctuaries were established. This purpose aligns directly with 'Conservation'. The text further emphasizes that the critical problem is the 'conservation of species' and mentions the 'world conservation strategy', confirming that these areas are established for conservation rather than recreation, hunting, or keeping pets.