The man vehemently denied all the charges of corruption that were levelled against him.

Answer: Option C

Devoutly : in a manner that shows deep religious feeling or commitment.
Hysterically : with wildly uncontrolled emotion.
Forcefully : in a strong and assertive manner; vigorously.
Serenely : in a calm, peaceful, and untroubled manner.
Vehemently : in a forceful, passionate, or intense manner; with great feeling.

Synonym of Vehemently is Forcefully