The ova are released by hormone induction and fertilization by artificial insemination and then embryo is stored at 4${}^o$C for several years. This technique is known as

The correct option is D Preservation of embryo
Embryo cryopreservation or preservation of embryo is generally performed as a component of in vitro fertilization which generally also include ovarian stimulation, ovarian hyperstimulation or superovulation, egg retrieval, artifical insemination and embryo transfer.