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
Which nucleus is not found in the floor of the fouh ventricle 
Select and explain. 
A. Abducens N, B. Dorsal vagal nuclei, C. Dorsal vagal nuclei, D. None
D: None
Answer: D: None 
Explanation: D i.e., None