This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Brainstem, cerebellum and ventricles, Subject name: Anatomy
Which one of the cranial nerves exits the brainstem from the posterior aspect? 
Select and explain. 
A. CN I, B. CN II, C. CN III, D. CN IV
D: CN IV
Answer: D: CN IV 
Explanation: Trochlear nerve (CN IV)is the only cranial nerve to exit the brainstem from the dorsal/ posterior aspect.