Option 1: provisional -> temporary or conditional, opposite of irrevocable.
Option 2: first -> refers to order or sequence, unrelated to permanence.
Option 3: irrefutable -> means undeniable or impossible to disprove, relates to arguments/truth rather than reversibility.
Option 4: final -> means conclusive and unchangeable, capturing the permanent nature of irrevocable.
Hence, Option 4: final -> "Irrevocable" means something that cannot be changed, reversed, or undone. "Final" is the closest synonym as it conveys the sense of permanence and conclusiveness, indicating that no further changes can be made -> correct