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': 'Commonest aery for cannulation is - \nSelect and explain. \nA. Radial, B. Ulnar, C. Brachial, D. Cubital', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Answer is \'a\' i.e. Radial "Aerial puncture and cannulation is performed to measure the Pa02, PaCO2, Sa02 and pH to clarify the acid-base and electrolyte status. Any aery that can be compressed after puncture may be used (but not end-aeries); usually the radial (preferred), brachial, or femoral" - Lee 12/e', 'role': 'assistant'}]