This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Maintenance of the corpus luteum during the first trimester of pregnancy is accomplished principally by the secretion of ? 
Select and explain. 
A. Antidiuretic hormone (ADH), B. Follicle stimulating hormone (FSH), C. Human chorionic gonadotropin (hCG), D. Luteinizing hormone (LH)
C: Human chorionic gonadotropin (hCG)
Answer: C: Human chorionic gonadotropin (hCG) 
Explanation: The corpus luteum secretes estrogens, progesterone, and relaxin. hCG, secreted by the syncytiotrophoblast lining the placental villi, maintains the corpus luteum during the first trimester of pregnancy. Antidiuretic hormone (vasopressin does not play a significant role during pregnancy. FSH acts on granulosa cells to promote the conversion of androstenedione to estradiol. LH acts on theca cells to promote androstenedione secretion. Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 22. Reproductive Development & Function of the Female Reproductive System. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong's Review of Medical Physiology, 24e.