This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Head and neck, Subject name: Anatomy
The superior oblique muscle is supplied by 
Select and explain. 
A. 3rd cranial nerve, B. 4th cranial nerve, C. 5th cranial nerve, D. 6th cranial nerve
B: 4th cranial nerve
Answer: B: 4th cranial nerve 
Explanation: Superior oblique muscle is supplied by fouh cranial nerve i.e,trochlear nerve. It supplies only the superior oblique muscle of the eyeball. Superior oblique muscle helps in depression,abduction and intoion. Note: When trochlear nerve is damaged, diplopia occur looking downwards; vision is single so long as the eye look above the horizontal plane. Ref:BDC 6th edition of no.208