💡 Detailed Explanation
The correct answer is '潔く' (isagiyoku). '潔い' means to be frank, decisive, and to face a difficult situation (like failure or defeat) without making excuses or showing regret. It perfectly fits the context of taking responsibility and resigning cleanly. '清々しく' (sugasugashiku) means 'refreshingly'. '雄々しく' (ooshiku) means 'bravely' or 'manfully', but lacks the nuance of accepting the outcome without complaint. '潔白に' (keppaku ni) means 'innocently', which contradicts the act of admitting responsibility.