This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Concepts in physiology, Subject name: Physiology
[{'content': 'Which of the following is NOT an example of ultrafiltration? \nSelect and explain. \nA. Filtration at systemic capillaries, B. Formation of CSF, C. Filtration at the glomerulus, D. Secretion of bile by hepatocytes', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ultrafiltration is filtration under pressure. Filtration at the systemic and glomerular capillaries are examples of ultrafiltration. Formation of CSF is paly ultrafiltration and paly by secretion of ependymal cells. Secretion of bile is an active process.', 'role': 'assistant'}]