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
Most common cause of bilateral internuclear ophthalmoplegia is 
Select and explain. 
A. Quinine toxicity, B. Diphtheria, C. Multiple sclerosis, D. Diabetes mellitus
C: Multiple sclerosis
Answer: C: Multiple sclerosis 
Explanation: U/L INO - Diabetes mellitus.
B/L INO - Multiple sclerosis.