Who came and visited Zoë that Enzo did not know?

The correct choice, which indicates that Denny's parents visited Zoë, is significant because Enzo, the narrator of the story, is particularly close to Denny and is protective of his family's dynamics. When Denny's parents arrive, it represents a shift in family interactions, influencing both the emotional landscape of the characters and Enzo's perception of the environment around him.

Denny's relationship with his parents is complex, which adds depth to the narrative. Enzo, being a dog who perceives human emotions and interactions, recognizes the impact this visit has on Denny and Zoë. Their presence introduces elements of tension and concern regarding family loyalty and support, which are recurring themes throughout the book.

Other options refer to different characters or situations that Enzo is aware of, either directly connected to Denny's immediate family or friends. However, the situation involving Denny's parents stands out as a pivotal moment Enzo perceives but is not fully privy to beforehand. This builds upon the overarching theme of communication and understanding within family units, highlighting Enzo's perspective as both a loyal companion and an observer of human circumstances.