This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anaesthesia For Special Situations, Subject name: Anaesthesia
A resident at the emergency department is preparing for a lumbar puncture in a 26 years old female with suspected subarachnoid bleeding. Although she presented with altered sensorium, CT brain was found to be normal. During LP, which structure is pierced after the spinal needle crosses interspinous ligament? 
Select and explain. 
A. Ligamentum flavum, B. Arachnoid membrane, C. Areolar tissue, D. Subarachnoid space
A: Ligamentum flavum
Answer: A: Ligamentum flavum 
Explanation: Ans: (a) Ligamentum flavumRef: Morgan's Clinical Anesthesiology, 5th edition, Chapter 16STRUCTURES PIERCED BY SPINAL NEEDLE DURING LP1. Skin2. Subcutaneous tissue3. Supraspinous ligament4. Interspinous ligament5. Ligamentum flavum6. Dura mater7. Arachnoid membrane