This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology and Reproduction, Subject name: Physiology
[{'content': 'Which vitamin acts as a hormone- \nSelect and explain. \nA. Niacin, B. Pyridoxin, C. Vitamin D, D. Riboflavin', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Vitamin D * Vitamin D and retinoic acid (Vitamin A) acts on endocrine intranuclear receptors and therefore are considered as hormonal Vitamin D.", 'role': 'assistant'}]