The word heal given in the bracket means to become sound or healthy again in other words to recuperate.
The adjective form of the verb heal would describe someone in a good physical or mental condition; in good health.
Option A: Is the noun form of the given verb. It means the ability to adapt and manage physical, mental and social challenges throughout life.
Option B: It is an adverb of the given verb form
Option C: Is an adjective form which means the same as the required meaning of the adjective.
Option D: Healthism is a neologism to describe a variety of ideological constructs concerning health and medicine. Not an adjective.
Option c is the correct choice.