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: Medicine
[{'content': 'Commonest site of the vermiform appendix is \nSelect and explain. \nA. Retrocaecal, B. Subcaecal, C. Pre-ilial, D. Post-ilial', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]