Which retail innovation, first widely implemented in 1937, revolutionized checkout efficiency and is considered one of the most important developments in retail history?

The history of retail has been marked by revolutionary innovations that transformed how people shop. One particular technological advancement in the early 20th century dramatically changed retail operations and customer experience, leading to the modern shopping environment we know today. This innovation eliminated a major bottleneck in retail transactions and paved the way for self-service models that define modern retail. Test your knowledge of this pivotal moment in retail history!

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The shopping cart (invented by Sylvan Goldman)
The cash register with automatic receipt printing (by NCR)
The supermarket checkout counter conveyor belt system
The pneumatic tube cash transport system (by Lamson Engineering)