The correct option is D diplomat
As given in the notes for the given context, Chanakya had the qualities of political shrewdness and diplomacy.
Here, in blank 4, the noun "diplomat" fits best as it indicates that Chanakya was a person who could deal with others in a sensitive and tactful way. Hence, option D is the correct answer.
Options A is incorrect "was born" does not fit the context and is ungrammatical.
Option B is incorrect as the verb "authored or wrote" does not fit the context.
Option C is incorrect as the adjective given in the context, "a great" is ungrammatically placed with the adjective "shrewd" .