Which detail contributes to the irony in “the colomber” by dino buzzati?

Choices:
“It’s the fish that sailors fear above all others . . . .”
“When Stefano Roi was twelve years old . . . .”
“‘Despite my forty years, . . . I believe I still have good eyesight.”
". . . as soon as he was a man, he found a dignified and well-paying position at an emporium . . . ."

The irony in "The Colomber" by Dino Buzzati is evident in this detail:

“It’s the fish that sailors fear above all others . . . .” 

It is believed to bring bad luck and doom the one who saw it. However, the Colomber appeared to Stefano because it was tasked to give him a pearl that will bring him good luck in life.