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: Pathology
[{'content': "Microcytosis is seen in - \nSelect and explain. \nA. Thalassemia, B. Hb Lepore, C. Hb bart's, D. All of the above", 'role': 'user'}, {'content': 'Answer: D \nExplanation: Causes of microcytosis (MCV < 80fl)\n• Iron deficiency anemia\n• Thalassemia\n• Sideroblastic anemia\n• Anemia of chronic disease\nIn Hb Barts, all the four a chain genes are deleted resulting in formation of Barts Hb.\nIn Hb Lepore, there is nonhomologus fusion of b and d genes and forms an abnormal hemoglobin with total absence of normal b chain. It is one of the form of b thalassemia minor.', 'role': 'assistant'}]