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: Pathology
Wernick's encephalopathy is caused by deficiency of 
Select and explain. 
A. Thiamine, B. Cyanocohalamine, C. Niacin, D. Riboflavin
A: Thiamine
Answer: A: Thiamine 
Explanation: None