Which excerpt from Kurt Vonnegut's "Report on the Barnhouse Effect" is an example of irony?

The correct answer for the question that is being presented above is this one: "B. At ten minutes before H-hour the general came in, shepherding the professor before him. The professor was comfortably attired in sneakers, gray flannels, a blue sweater, and a white shirt open at the neck."

Here are the following choices:

A. Professor Barnhouse closed his eyes, pursed his lips, and stroked his temples. He held the position for a minute.

B. At ten minutes before H-hour the general came in, shepherding the professor before him. The professor was comfortably attired in sneakers, gray flannels, a blue sweater, and a white shirt open at the neck.

C. The tenth still told me nothing. It was only last night that I discovered how it fitted in with the rest. The sentence appeared in my thoughts last night, while I was toying absently with the professor's dice.

D. Dutifully and fearfully I watched. A high-pitched humming seemed to come from the inkwell; then it began to vibrate alarmingly.