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: Surgery
[{'content': 'All of the following are true about aortic aneurism except \nSelect and explain. \nA. Saccular aneurism involves whole circumference, B. True aneurism involves all 3 layers, C. Atherosclerosis is the commonest cause, D. False aneurism is not covered by all 3 layers', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]