Which linguistic principle is Duolingo primarily leveraging in their slogan 'Learn a language for free. Forever.'?

In the world of language and linguistics, brands often employ sophisticated linguistic techniques to create memorable slogans and names. This poll tests your knowledge of how language science informs brand identity in the linguistics industry. From phonological patterns to semantic associations, see if you can identify which linguistic principle is at work in a famous language learning brand's slogan.

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Alliteration with the repeated 'f' sound for memorability
Syntactic parallelism through balanced phrase structure
Semantic priming with language acquisition terminology
Morphological compounding to create novel word forms