Final answer:
Mrs. Clara Post, as referred to in the dialogue, was a neighbor from Baltimore, indicating a previous close living proximity and a likely personal connection.
Step-by-step explanation:
Based on the context provided by the dialogue, it appears that Mrs. Clara Post is a character who was previously a neighbor from Baltimore. The statement from Christine specifically mentions a past living situation and refers to Mrs. Post with familiarity, suggesting that they were neighbors at the time when Christine was living in Baltimore. Therefore, the correct answer is b) A neighbor from Baltimore.