The sperms employed for artificial insemination of cattle are stored in ___________.
A.Liquid oxygen
B.Dry ice
C.Liquid ammonia
D.Liquid nitrogen

Hint: The process is known as cryopreservation. Artificial insemination (AI) is a globally accepted method of breeding cattle. It is highly effective for other species like goats, and other mammals that are needed for immediate conservation. An estimated 150 million cows are artificially inseminated annually worldwide.

Complete answer:
Semen is the male ejaculate. It can be stored deep-frozen in liquid nitrogen at –96 degrees Celsius. This process is known as cryopreservation Cryopreservation is also used in the field of biochemistry and genetics for recombination reactions, etc.
The artificially ejaculated semen from desirable male (with desirable genetic makeup) is stored for long periods of time before inseminated into the female genital tract
If insemination is not a viable option, the eggs are obtained artificially from the ovaries of the females. After this, the eggs are fertilized externally in a petri dish. This process is known as in-vitro fertilization (IVF). After this, the zygote (8- celled stage) is transferred to the endometrium of the uterus. This process is known as intrauterine transfer.

Therefore, Option D Liquid nitrogen is correct.

Note:
Dry ice is the solid form of carbon dioxide. It is used as a cooling agent primarily. It has the following uses/ advantages:
-It is of lower temperature than that of normal water ice
-It doesn’t leave any residue
-It is useful for preserving frozen food products where mechanical cooling is not a viable option.
-Liquid oxygen is used as an oxidant for liquid fuels like ethanol, petrol, etc. in the propellant systems of missiles and rockets.
-Ammonia is used as a refrigerant gas for the purification of water. It is also used in the manufacture of plastics, explosives, textiles, pesticides, dyes, and other chemicals.