Which retail innovation, first introduced in 1916, fundamentally transformed shopping by allowing customers to select their own merchandise without clerk assistance?

The retail landscape we know today emerged through centuries of innovation. From humble market stalls to department stores and beyond, retail history showcases humanity's evolving relationship with commerce. This trivia question focuses on a pivotal moment in retail history that fundamentally changed how people shopped and influenced store designs we still see today. Test your knowledge of retail innovation history!

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The shopping cart (invented by Sylvan Goldman)
The self-service grocery store (pioneered by Piggly Wiggly)
The department store elevator (championed by Marshall Field)
The cash register (patented by James Ritty)