Correct Option: A

Cryogenic engines are specially designed to carry out combination of cryogenic fuels. Cryogenic fuels are cooled liquefied gaseous fuels. Cryogenic engines are used in rockets, so they are also known as 'Cryogenic rocket engines'. Generally, liquefied and cooled hydrogen and oxygen in combination are used as Cryogenic propellant in rockets Now-a-days propelled rocket engines are having a great demand in the field of apace exploration as they provide high specific impulse during the ignition spacecraft's engine.