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: Physiology
[{'content': 'Hemoglobin is present in: \nSelect and explain. \nA. Hydrophilic pockets, B. Hydrophobic pockets, C. Pyrrole rings, D. Cationic ring', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Hydrophobic pockets', 'role': 'assistant'}]