Option 1 -> Untruthful means false or dishonest, which relates to accuracy rather than style.
Option 2 -> Vituperative means bitter and abusive in language, describing harsh criticism rather than pretentiousness.
Option 3 -> Austere means simple and unadorned, which is the opposite of high-flown and pretentious.
Option 4 -> Bombastic means pompous and inflated in style, using high-sounding language with little substance.
Hence, Option 4: bombastic -> The word "bombastic" perfectly captures speech that is high-flown and pretentious, as it specifically refers to language that is pompous, inflated, and excessively grandiose. This directly aligns with the orator's style described in the question. -> correct