This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Spinal, Epidural, & Caudal Blocks, Subject name: Anaesthesia
[{'content': "Success of Block 1 is assessed by \nSelect and explain. \nA. Westphal's sign, B. Gutierrez sign, C. Loss of resistance, D. Crawford sign", 'role': 'user'}, {'content': "Answer: A \nExplanation: Westphal's sign (Block 1 is Epidural block)", 'role': 'assistant'}]