Which word is not a synonym for the word vernacular?
vernacular means the language spoken by the ordinary people of a country or region
Option C is indigent which means poor or needy. For example, we do charity for indigent person. So, it is not a synonym for the word vernacular.
Option A also relates in some sense because it means relating to a region and same for colloquial means language used informally in a particular region and same thing for B also.
CORRECT ANSWER IS C.