Final answer:
The primary theme of the story is that there is more depth to individuals than is readily apparent on the surface. This is exemplified by Sophia's discovery of her great-aunt's secret life as a children's book author and illustrator.
Step-by-step explanation:
The main theme or lesson of the story about Sophia and her great-aunt is the realization that people have more depth than their outward appearance or behavior might suggest. The discovery in the attic reveals Aunt Jane's untold story as a talented artist and author, challenging the mundane perception Sophia had of her. This theme is a reflection of a broader understanding that often unfolds in literature, where characters discover unexpected qualities or pasts of others, leading to a richer understanding of their identities and stories.
C. There’s a lot more to people than what you see on the surface
is the best description of the main theme of the story because it encapsulates the surprising discovery made by Sophia that her great aunt, who appeared to be a stony-faced and silent woman, had a secret life as a beloved children's book author and illustrator. Hence, the story emphasizes the lesson that we should look beyond the surface level to truly understand people and their contributions.