Concrete nouns are nouns which can be experienced through one/more of our five senses viz. sight, smell, hearing, touch and taste.
Option A: The word "he" is a pronoun and not a noun.
Option B: The word "honest" qualifies/ defines the noun "man". Hence, it is an adjective and is not the correct answer.
Option C: The word "man" is a common noun. It means a person (a male), who can be seen. Hence, this is a concrete noun. This is the correct answer.
Option D: Incorrect as Option C is the correct answer.