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: Orthopaedics
After L4- S1 the next commonest site of intervertebral disc prolapse is - 
Select and explain. 
A. C6 - C7, B. T12 - LI, C. L1- L2, D. L2 - L3
A: C6 - C7
Answer: A: C6 - C7 
Explanation: L5 and L4 - L5 level → 80%.
C5 - C6 and C6–7 level → 19-20%.