The correct option is C Cryopreservation
In situ conservation is the type of biodiversity conservation in which the whole ecosystem is conserved on site or in their natural habitat. Examples - biodiversity hotspots, sacred groves, sanctuaries, national parks etc.
Cryopreservation is a technique in which cells, tissues or organs are preserved by cooling them at a very low temperature by normally using liquid nitrogen at around −196οC. This is a type of ex situ conservation.
Usually, gametes of threatened species are preserved for a long duration of time in viable and fertile conditions using this technique of cryopreservation.