Which innovative retail approach was first pioneered by military exchanges (PX/BX) during WWII that later became standard practice in civilian retail chains?

Military exchanges (PX/BX) have evolved significantly to serve military personnel and their families worldwide. These unique retail operations combine commercial practices with military mission support. This poll tests your knowledge of how military retail operations have innovated to maintain customer retention and relevance throughout history, providing essential services to those who serve.

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Self-service shopping format (customers selecting their own merchandise)
Loyalty card programs with tiered benefits based on rank
Online ordering with base delivery (pre-internet catalog system)
Integrated food courts within retail shopping spaces