A. second or third
Example:
Every good homeowner plays their part in keeping the neighborhood clean and safe.
Antecedent: every good homeowner
Pronoun: their (which is incorrect because "every homeowner" is singular)
For singular antecedents, we should use singular pronouns. Singular pronouns include: I, he, she, it, and you. Since this refers to a second person (every homeowner), we can't use "I", "it", and "you". Hence, we can use "he" or "she" instead.
CORRECT SENTENCE: Every good homeowner plays his/her part in keeping the neighborhood clean and safe.