Final answer:
Chaucer wrote the Canterbury Tales in vernacular to capture the rhythm of everyday speech and make his work accessible to a wider audience.
Step-by-step explanation:
Chaucer wrote the Canterbury Tales in vernacular because he managed to capture the rhythm of everyday speech. Unlike many writers of his time who wrote in a poetic language designed for recital, Chaucer chose to use the language spoken by the common people. This helped make his work accessible and relatable to a wider audience.