The correct answer is B. He himself wrote the 20-page paper.
Step-by-step explanation:
Pronouns such as himself, yourself, themselves, or myself, which are known as intensive pronouns, are used to emphasize the subject of a sentence, usually by placing the pronoun right the subject or main pronoun. This can be seen in the sentence "He himself wrote the 20-page paper" because the pronoun "himself" emphasizes the action "wrote" performed by "he", which is the main subject of the sentence. According to this, it is in the second sentence a pronoun creates emphasis.