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: Anatomy
Dermatomal supply of the perianal skin is - 
Select and explain. 
A. S1, B. L2, C. L3, D. S4
D: S4
Answer: D: S4 
Explanation: Dermatomal supply of perianal skin and groin is S4.