Which packaging innovation was originally developed for military use during WWII and revolutionized how combat rations were preserved and distributed to troops?

Throughout military history, packaging design has played a crucial but often overlooked role in warfare. From preserving rations to protecting ammunition, innovative packaging solutions have sometimes made the difference between victory and defeat. This trivia question explores one of the most significant packaging innovations that changed modern military logistics and influenced civilian product packaging worldwide.

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The SPAM can with attached key opener
The retort pouch (flexible packaging that could be heat-sterilized)
The pull-tab aluminum can
Vacuum-sealed glass jars with metal lids