Explanation:
Geoffrey Chaucer is credited with several literary innovations, including the use of vernacular language in literature, the creation of the modern English poetic form, and the development of the frame narrative structure. Chaucer’s use of vernacular language in The Canterbury Tales, instead of the traditional Latin, made literature accessible to a broader audience and helped establish English as a literary language. The use of frame narrative structure, where a group of pilgrims tell stories within a larger narrative framework, was a significant innovation that influenced later writers. Therefore, the innovation attributed to Geoffrey Chaucer is the development of the frame narrative structure.