Final answer:
Montresor mocks Fortunato when Fortunato realizes the gravity of his situation.
Step-by-step explanation:
Once Fortunato realizes the gravity of his situation, he loudly rattles his chains. In response, Montresor mocks Fortunato.
When Montresor hears Fortunato's pleas for help, he does not show any sympathy or try to comfort him. Instead, Montresor continues with his plans and taunts Fortunato, enjoying his torment.
This reaction highlights Montresor's cruel and sadistic nature, as he takes pleasure in Fortunato's suffering.