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': 'Which of the following is the most sensitive for detection of iron depletion in pregnancy: March 2013 \nSelect and explain. \nA. Serum iron, B. Serum transferrin, C. Serum erythropoitein, D. Serum ferritin', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. D i.e. Serum ferritin', 'role': 'assistant'}]