The correct option is B Seed bank
In-situ conservation: When we conserve and protect the whole ecosystem, its biodiversity at all levels is protected and we save the entire ecosyatem. This approach is called in-situ (on-site) conservation. Example - biosphere reserves, national parks, biodiversity hotspots, sanctuaries, etc.
Ex-situ conservation: In this approach, animals and plants species are taken out from their natural habitat and placed in special setting where they can be protected and given special care. Seed bank is one such example.