This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Blood, Subject name: Pathology
[{'content': 'Earliest response to iron therapy is:(1995) \nSelect and explain. \nA. Increase in Hb%, B. Reticulocytes, C. Increased PCV, D. Increased neutrophils', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans: b', 'role': 'assistant'}]