Which WWII military innovation directly led to the development of microwave ovens, now a staple product in retail stores worldwide?

Many of today's retail technologies and product innovations have surprising origins in military history. From RFID tracking to the internet itself, military R&D has transformed how products are sold and marketed worldwide. This poll tests your knowledge about a specific military innovation that revolutionized the retail landscape and created entirely new product categories. Can you identify which wartime development led to this transformative retail technology?

This is a live public trivia poll on AIPolls.Net. Vote and see real-time results.

Radar technology using magnetrons (cavity magnetron)
Radio encryption systems (Enigma machine)
Sonar detection systems (ASDIC)
Aircraft pressurization technology