The poetic art of Keats reached consummation at the end of his poetic career.

Answer: Option C

Failure : lack of success.
Deterioration : the process of becoming progressively worse.
Completion : the action or process of completing or finishing something.
Frivolity : lack of seriousness; light-heartedness.
Consummation : the point at which something is complete or finalized.

Synonym of Consummation is Completion