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': "Poiseuille's law is \nSelect and explain. \nA. F = (PA – PB) πr4/8nL, B. F = (PA x PB) πr4/8nL, C. F = (PA + PB) πr4/8nL, D. F = (PA / PB) πr4/8nL", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]