In semen banks, semen is preserved at low temperature using:

Ans. is c, i.e. Liquid nitrogenRef: Jeffcoate 7th/ed, p723Cryopreservation of semen:Involves cooling of embryos in the pronucleate stage or early cleavage stage to very low temperature in the presence of cryoprotectants such as:* I2 - Propanediol (Iodine)* Glycerol* Dimethyl sulphoxide (DMSO) with sucrose.* They are then stored in liquid nitrogen till required.Q* Over half the embryos survive thawing process.