Choose the correct option for the following underlined phrase:-A high…

The correct answer is Option (1) → Bombastic

Bombastic describes speech or writing full of grand, inflated words used to sound important, that is, high-flown and pretentious. The word comes from bombast, cotton wool once used to pad clothes: such speech is "padded" with big words.
Example: The minister's bombastic speech said very little.

Why the Other Options are Incorrect?

Option 2: Austere — Incorrect. Austere means plain, strict and without luxury or decoration; it is almost the opposite of high-flown.
Example: The monk led an austere life.

Option 3: Vituperative — Incorrect. Vituperative means full of bitter and abusive criticism; such speech is angry, not pretentious.
Example: The editor wrote a vituperative attack on the policy.

Option 4: Eulogy — Incorrect. A eulogy is a speech of high praise, often given at a funeral; it names a kind of speech by its purpose, not a pretentious style.
Example: He delivered a moving eulogy for his teacher.