42. How has the scientific understanding of nostalgia shifted since the 17th century? (A) It is now recognized as a physical ailment rather than a psychological one. (B) It is now considered a primary cause of existential dread and loneliness. (C) It has been proven to be a permanent barrier to personal growth and self-continuity. (D) It has transitioned from being viewed as a detrimental illness to a beneficial psychological coping mechanism.