Cryogenic engines are used

The correct answer is [C] In rocket technology. Cryogenic engines are utilized in rocket propulsion systems. These engines employ extremely low temperatures, typically below -150°C, to store and handle propellants like liquid hydrogen or liquid oxygen. The cryogenic temperatures allow for higher fuel densities and efficiencies, resulting in greater thrust and payload capacity for rockets. This technology is crucial for launching spacecraft into orbit and beyond, as it provides the necessary propulsion power for space exploration missions. While cryogenic temperatures are also utilized in research on superconductivity, submarine propulsion typically relies on nuclear or conventional engines, and frost-free refrigerators utilize different cooling mechanisms. Therefore, cryogenic engines find their primary application in rocket technology, facilitating space exploration and enabling advancements in satellite deployment, interplanetary travel, and scientific research in space.