Which phrase in this excerpt from Kurt Vonnegut's "Report on the Barnhouse Effect" is an example of sarcasm?

The phrase that is an example of sarcasm in the excerpt from "Report on the Barnhouse Effect," by Kurt Vonnegut is:

"To ask how much longer the professor will live is to ask how much longer we must wait for the blessings of another world war."

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Which phrase in this excerpt from Kurt Vonnegut's "Report on the Barnhouse Effect" is an example of sarcasm?

To ask how much longer the professor will live is to ask how much longer we must wait for the blessings of another world war. He is of short-lived stock: his mother lived to be fifty-three, his father to be forty-nine; and the life-spans of his grandparents on both sides were of the same order. He might be expected live, then, for perhaps fifteen years more, if he can remain hidden from his enemies. When one considers the number and vigor of these enemies, however, fifteen years seems an extraordinary length of time, which might better be revised to fifteen days, hours, or minutes. The professor knows that he cannot live much longer. I say this because of the message left in my mailbox on Christmas Eve. Unsigned, typewritten on a soiled scrap of paper, the note consisted of ten sentences. The first nine of these, each a bewildering tangle of psychological jargon and references to obscure texts, made no sense to me at first reading. The tenth, unlike the rest, was simply constructed and contained no large words.

To ask how much longer the professor will live is to ask how much longer we must wait for the blessings of another world war.

Explanation:

Sarcasm is simply defined as using irony to mock or ridicule something or someone.

From this excerpt of Kurt Vonnegut's "Report on the Barnhouse Effect". the phrase that is used which is an example of sarcasm is To ask how much longer the professor will live is to ask how much longer we must wait for the blessings of another world war.

War is not a blessing, so the narrator used that word to show irony to probably convey contempt. Also, he also means that no one knows how long the professor will live because it is as uncertain as knowing when a world war will start.

"blessings" being the key word, because a world war would not bring blessings, but devastation.