This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
[{'content': 'Haemoglobin first appears in which stage of erythropoiesis? \nSelect and explain. \nA. Basophil erythroblast, B. Proerythroblast, C. Ohochromatic erythroblast, D. Polychromatophil erythroblast', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Once the proerythroblast has been formed, it divides multiple times, eventually forming many mature RBCs. The first-generation cells are called basophil erythroblasts because they stain with basic dyes; the cell at this time has accumulated very little hemoglobin.', 'role': 'assistant'}]