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: Anaesthesia
Onset of post spinal headache is usually at hours after spinal anesthesia 
Select and explain. 
A. 0 - 6, B. 12-Jun, C. Dec-72, D. 72 - 96
C: Dec-72
Answer: C: Dec-72 
Explanation: Ans. is 'c' i.e., 12 - 72