Which groundbreaking feature did Duolingo first introduce in their subscription model that revolutionized language learning apps?

In recent years, language technology companies have revolutionized how we access linguistic tools through subscription models. From translation services to grammar checkers, these platforms have transformed both casual and professional language use. This poll tests your knowledge about a significant development in how language learning subscription services evolved to meet consumer demands through innovative product features.

This is a live public trivia poll on AIPolls.Net. Vote and see real-time results.

Offline mode for learning without internet connection
Hearts system with a limited number of mistakes per day for free users
AI-powered pronunciation feedback using speech recognition
Personalized vocabulary lists based on user profession