Final answer:
The illiteracy of Mrs. Grose in a literary work may signify her lower socio-economic status, contrast intellectual levels among characters, and act as an obstacle to solving mysteries within the narrative.
Step-by-step explanation:
The depiction of Mrs. Grose as illiterate could serve several narrative purposes in a literary work. Her illiteracy may represent social and economic class divisions inherent during the time period the story is set in, emphasizing her lower socio-economic status and dependency within the household. It could also function as a tool to contrast other characters' literacy, highlighting intellectual disparities and access to knowledge. Moreover, it might stand as an obstacle to the unravelling of the story's mystery, where crucial information could be hiding within written texts which Mrs. Grose is unable to decipher. This emphasizes the power of language and education, and how their absence can affect agency and understanding within the storyline.