Answer:
The answer to your question would be that the personal pronoun that completes the sentence correctly is the following one: Their.
Step-by-step explanation:
The sentence above is an example of the use of singular they. Singular they is the use of the pronoun they or any of its derivative forms (their, theirs, them, themselves) as a gender-neutral singular pronoun. This use typically occurs with unspecified antecedents. For instance, the antecedent in the sentence in question is everyone, an indefinite pronoun. Consequently, singular they refers back to "everyone", everyone who can either be a woman or a man.