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
All of the following are present beneath floor of 4th ventricle except 
Select and explain. 
A. Hypoglossal nucleus, B. Facial nucleus, C. Abducens nucleus, D. Facial nerve
B: Facial nucleus
Answer: B: Facial nucleus 
Explanation: Facial colliculus, a swelling in floor of 4th ventricle is formed by facial nerve looping around abducens nucleus. So facial nucleus doesn’t form the floor of 4th ventricle.