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: Gynaecology & Obstetrics
[{'content': 'Dietary supplement alone can not compensate for the increased requirement of which nutrient in pregnant women : \nSelect and explain. \nA. Iron, B. Iodine, C. Magnesium, D. Calcium', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Iron', 'role': 'assistant'}]