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
Success of Block 1 is assessed by 
Select and explain. 
A. Westphal's sign, B. Gutierrez sign, C. Loss of resistance, D. Crawford sign
A: Westphal's sign
Answer: A: Westphal's sign 
Explanation: Westphal's sign (Block 1 is Epidural block)