I do not desire to live to distrust.-I have the heart and stomach of a king.-I myself will be your general, judge, and rewarder.
"B. dark humor and paranoid characters" is correct. Postmodern literature was famous for its unusual story lines and crazy plot twists, that were almost always unrealistic.
I think the dominant irony presented in the passage would be :
The Houyhnhnms. the most rational beings on earth, are discussing the extermination of an entire group of creatures.
You can see that in this sentence, the second part of the statement contradict the statement on the first part.
I hope you can get your answers