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: Social & Preventive Medicine
[{'content': "1st symptom of vitamin A deficiency: March 2009 \nSelect and explain. \nA. Conjunctival xerosis, B. Bitot's spots, C. Night blindness, D. Corneal ulcer", 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. C: Night blindness Vitamin A deficiency is common in developing countries but rarely seen in developed countries. Night blindness is one of the first signs of vitamin A deficiency. Xerophthalmia and complete blindness can also occur since Vitamin A has a major role in phototransduction. Vitamin A deficiency also diminishes the ability to fight infections. In countries where children are not immunized, infectious disease like measles, have higher fatality rates. Even mild, subclinical deficiency can also be a problem, as it may increase children's risk of developing respiratory and diarrheal infections, decrease growth rate, slow bone development and decrease likelihood of survival from serious illness.", 'role': 'assistant'}]