Which of the following symptoms is characteristic of borderline personality disorder?

A) Hallucinations
B) Manic behavior
C) Major depressive episodes
D) Unstable relationships

Unstable relationships are a characteristic symptom of borderline personality disorder, as individuals with this disorder often struggle with intense and unstable relationships, including fear of abandonment and difficulty maintaining close connections with others. The other symptoms listed (hallucinations, manic behavior, and major depressive episodes) may be present in other mental health disorders, but are not necessarily characteristic of borderline personality disorder.