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: Biochemistry
[{'content': "1st clinical sign of vitamin A deficiency is \nSelect and explain. \nA. night blindness, B. bitot's spots, C. xerostomia, D. conjunctival xerosis", 'role': 'user'}, {'content': 'Answer: D \nExplanation: Night blindness (nyctalopia) is\xa0 one\xa0 of\xa0 the\xa0 earliest symptoms\xa0 of\xa0 vitamin\xa0 A\xa0 deficiency.', 'role': 'assistant'}]