Answer: A. The use of words such as "unsustainable" and "unrecoverable" helps establish a formal style.
Explanation: Some speeches, like in the extract showed above, displayed a formal style is a broad term for a speech or a text document characterized by a precise use of language, often impersonal and objective. The use of antonyms like "unsustainable" and "unrecoverable" reinforce such style.
