Option (D) is correct because national parks and sanctuaries are established for the purpose of conservation. National park and sanctuaries provide a specific place where animals are kept in captivity in order to preserve the species.

Option (A) is not correct because recreation activities are done for enjoyment, pleasure and fun but natural parks and sanctuaries are not established for the purpose of recreation. It is mainly established for protecting the wild animal and conserving the natural world.

Option (B) is not correct because hunting of animals causes loss of wild life animals.

Option (C) is not correct because national parks and sanctuaries are mainly built for wildlife animals not for pets.