Which packaging innovation, first widely deployed during WWII, revolutionized military field rations by allowing troops to heat meals without revealing their position through smoke or flame?

Product packaging has been crucial in military history, especially for field rations. Throughout conflicts, nations have innovated packaging to ensure soldiers receive adequate nutrition in extreme conditions. From the American Civil War's hardtack boxes to modern MREs (Meals, Ready-to-Eat), packaging evolution reflects both technological advancement and changing understanding of combat nutrition needs. This poll tests your knowledge about a significant packaging innovation that revolutionized battlefield sustenance during World War II.

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The Flameless Ration Heater (FRH)
The K-Ration's waxed cardboard containers
Vacuum-sealed tin cans with pull-tabs
Self-heating cans using calcium oxide reaction