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: Ophthalmology
Superior oblique muscle is supplied by: March 2005 
Select and explain. 
A. Third cranial nerve, B. Fouh cranial nerve, C. Fifth cranial nerve, D. Sixth cranial nerve
B: Fouh cranial nerve
Answer: B: Fouh cranial nerve 
Explanation: Ans. B: Fouh cranial nerveEach extraocular muscle is innervated by a specific cranial nerve:Medial rectus (MR) -- cranial nerve III (Oculomotor)Lateral rectus (LR) -- cranial nerve VI (Abducens)Superior rectus (SR) -- cranial nerve III (Oculomotor)Inferior rectus (IR) -- cranial nerve III (Oculomotor)Superior oblique (SO)--cranial nerve IV (Trochlear)Inferior oblique (I0) --cranial nerve III (Oculomotor) The following can be used to remember the cranial nerve innervations of the six extraocular muscles:LR6 (SO4)3.That is, the lateral rectus (LR) is innervated by C.N. 6, the superior oblique (SO) is innervated by C.N. 4, and the four remaining muscles (MR, SR, IR, and RD) are innervated by C.N. 3.