Which language learning product famously launched with the innovative marketing tagline 'The fastest way to learn a language guaranteed®' and pioneered the subscription-based model for language acquisition?

Throughout history, language learning products have transformed how we approach new languages. Some product launches revolutionized the industry with innovative approaches, while others created entirely new markets. This trivia question tests your knowledge about a significant product launch that changed language learning forever. Can you identify which language learning product had the most revolutionary launch strategy?

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Rosetta Stone, which initially sold physical CD sets before moving to a subscription model in 2017
Pimsleur, which launched with a focus on audio-based learning through graduated interval recall
Duolingo, which launched as a completely free service with gamification elements and a freemium model
Babbel, which was the first language learning application to fully embrace the subscription-based model from launch in 2007