Which product design innovation first allowed dictionary users to hear the pronunciation of words rather than just reading phonetic spellings?

Dictionaries have evolved dramatically from physical books to digital tools that shape how we communicate. Their product design reflects changing consumer needs, technological capabilities, and linguistic trends. This poll tests your knowledge about a significant innovation in dictionary product design that revolutionized how people interact with language resources.

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CD-ROM dictionaries with audio files (first introduced by Random House Webster's Electronic Dictionary in 1990)
Online subscription-based dictionaries (first introduced by Oxford English Dictionary in 1988)
Handheld electronic dictionaries (first introduced by Franklin Electronic Publishers in 1986)
Dictionary mobile apps with voice output (first introduced by Dictionary.com in 2001)