If I understand the question, you are supposed to choose one of the four quotes as the best example of foreshadowing and then explain why. I would say that the first quote is the best: "You are a man to be missed."

Montresor has made it plain that he intends to kill Fortunato. He has thought about every aspect of his revenge. He specifies early in the story that he must commit the murder with impunity.

AT LENGTH I would be avenged; this was a point definitively settled-- but the very defnitiveness with which it was resolved precluded the idea of risk. I must not only punish, but punish with impunity.

This means that he has thought about what will inevitably happen after Fortunato has vanished. There will be a huge inquiry because he is an important citizen. Montresor will not be suspected because he has taken pains to make everyone believe that he and Fortunato are the best of friends.

It must be understood that neither by word nor deed had I given Fortunato cause to doubt my good will. I continued as was my wont, to smile in his face, and he did not perceive that my smile NOW was at the thought of his immolation.

Montresor, however, will have to act especially concerned about the mysterious disappearance. He may have to keep up this pretense for as long as the investigation continues and it remains a topic of speculation and conversation. No doubt he will enjoy doing so, since he is an expert at dissimulation.

Montresor's heart is so full of hatred and hunger for vengeance that he even enjoys the thought of the emotions that Fortunato's loved ones will undergo for a long time after his disappearance. When Montresor says, "You are a man to be missed," he is thinking about the future. He knows that Fortunato will be missed by his wife and many other people, and he anticipates getting the additional satisfaction of inflicting further vengeance on Fortunato by inflicting lingering distress on his relatives and friends. The "not knowing" will be an especially sadistic kind of pain, and Montresor has thought about this aspect of his revenge along with every other detail of his scheme.

The foreshadowing in connection with the quote "You are a man to be missed" is not a foreshadowing of the actual murder but a foreshadowing of the aftermath of the murder. Montresor has guaranteed his own "impunity" by counterfeiting frendship for his intended victim. He has been calling his his friend and his good friend, presumably for years. He has gotten so accustomed to this that he continues referring to him as "my friend," "my good friend," and "my poor friend" throughout his narrative. For example:

The gait of my friend was unsteady, and the bells upon his cap jingled as he strode.

My poor friend found it impossible to reply for many minutes.

Montresor is not being ironic. He hates Fortunato but for his own future safety he has conditioned himself to thinking of him as his friend. This will assure his freedom from the slightest shred of suspicion when the outcry over Fortunato's disappearance and the inevitable police investigation begin. Montresor has no fears about the future. He is actually looking forward to the aftermath of his crime. This is what he is thinking about when he tells his "friend,"

"You are a man to be missed."