In Poe’s “The Cask of Amontillado” , which of the following makes Montresor an unreliable narrator?

He is part of a secret association.

He makes exaggerated claims about Fortunato.

He does not offer any possible reason for wanting to murder Fortunato.

He makes exaggerated claims about Fortunato.

are you very sure

Yes, I am sure. Montresor's exaggerated claims about Fortunato's expertise in wines and his exaggerated flattery towards him suggest that he may not be completely honest in his narration. This adds to his unreliability as a narrator.