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
Paralysisof 3rd, 4th, 6th nerves with involvement of ophthalmicdivisionof5thnerve, localizes the lesion to 
Select and explain. 
A. Apex of orbit, B. Brainstem, C. Cavernous sinus, D. Base of skull
C: Cavernous sinus
Answer: C: Cavernous sinus 
Explanation: Ipsilateral ophthalmoplegia  causing diplopia occur due to 3rd, 4th  & 6th cranial nerves.
6th nerve passes through cavernous sinus and others are related to the lateral wall of cavernous sinuses.