The correct answer is D. Sanctuaries.
Sanctuaries are areas of land or water that are set aside for the protection of wildlife. They are usually managed by government agencies or non-profit organizations, and they provide a safe haven for animals and plants that are threatened or endangered.
Zoos, botanical gardens, and national parks are also important for conservation, but they serve different purposes than sanctuaries. Zoos are primarily educational institutions, and they often focus on breeding endangered species. Botanical gardens are dedicated to the study and conservation of plants, and they often have large collections of rare and endangered species. National parks are protected areas of land that are managed for their natural beauty and for the benefit of the public.
Sanctuaries are the best place to protect animals and plants because they provide a safe and undisturbed environment where they can live and reproduce without the threat of hunting, habitat loss, or other human activities.