This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ear, Subject name: ENT
All of the following conditions will produce nystagmus to left except: 
Select and explain. 
A. Irrigation of left ear with cold water, B. Purulent labyrinthitis on the right side, C. Irrigation of right ear with cold water, D. Irrigation of left ear with warm water
A: Irrigation of left ear with cold water
Answer: A: Irrigation of left ear with cold water 
Explanation: Irrigation of left ear with cold water will cause nystagmus to the right. Here the student should remember the acronym COWS, i.e. Cold water causes nystagmus to Opposite side and Warm water to the Same side. Thus irrigation of right ear with cold water and irrigation of left ear with warm water will cause nystagmus to left. Similarly purulent labyrinthitis on right side causes nystagmus to left as purulent labyrinthitis makes labyrinth dead (or hypoactive as in cold water irrigation).