A man is as ....... as he feels
B
Correct answer
Explanation
The complete saying is 'A man is as old as he feels,' meaning age is more about mindset and health than chronological years. 'Old' is the correct word to complete this proverb. 'Young' would contradict the saying's meaning about aging being subjective. 'Smart' and 'clever' are irrelevant to this wisdom about age perception.