Choose the correct pronoun: He himself left the field.

Pronouns are words used as substitutes for nouns in a sentence. We can roughly categorize pronouns into eight main categories. The pronouns we use to ask a question are called Interrogative Pronouns. Pronouns that do not refer to anything specifically are called Indefinite Pronouns. Relative Pronouns refer to nouns previously applied in the sentences. The pronouns that are used when the subject and the object of a verb in a sentence are the same are called Reflexive Pronouns. We can clearly see this tendency in the mentioned sentence. So option D is the correct one.