Which advertising campaign fundamentally changed language learning product marketing by introducing the concept of 'spaced repetition' to mainstream consumers?

In the world of language products and services, advertising campaigns often make bold claims about effectiveness and results. This poll tests your knowledge about a famous advertising campaign that transformed how language learning products were marketed to consumers and created a new standard in the industry. Can you identify which campaign truly revolutionized language product marketing?

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Rosetta Stone's 'The Fastest Way to Learn a Language' (2006)
Pimsleur's 'Learn Like a Child' (1999)
Duolingo's 'Free Language Education for the World' (2012)
SuperMemo's 'Remember Forever' (1991)