Explanation
Among the given options, (D) Gene banks is an ex situ method of conservation.
Gene banks, also known as seed banks or genetic resource banks, are facilities that store and preserve genetic material, such as seeds, plant tissue samples, or reproductive cells, of various plant and animal species. These banks serve as repositories of genetic diversity, providing a means to conserve and protect genetic resources for future use.
Gene banks play a crucial role in preserving the genetic diversity of species, including rare and endangered ones, outside their natural habitat. The stored genetic material can be used for research, breeding programs, and conservation efforts to maintain and restore populations of threatened species.
On the other hand, biosphere reserves, wildlife sanctuaries, and national parks are primarily in situ methods of conservation. They involve the protection and management of species and their habitats within their natural ecosystems.