|A) Frost - Free refrigerators||B) Sub-marine propulsion|
|C) Researches in superconductivity||D) Rocket technology|
Answer: D) Rocket technology
Cryogenic Engines find applications in Rocket technology. A cryogenic rocket engine is a rocket engine that uses a cryogenic fuel or oxidizer, that is, its fuel or oxidizer are gases liquefied and stored at very low temperatures. Notably, these engines were one of the main factors of NASA's success in reaching the Moon by the Saturn V rocket.