Why does Montresor wait for a reply before he puts the last stone in position? What do you think he wants Fortunato to say?

Montresor, like most of Poe's protagonists, is twisted. He wants to hear id Fortunado is dead or not. He wants to hear one last plea for help. Montresor wants the validation that he has indeed made his "nemesis" (though we really don't know what he did that was so bad) suffer.