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: Pharmacology
Dilantain (Phenytoin) is known to cause: 
Select and explain. 
A. Folic acid deficiency, B. Biotin deficiency, C. Thiamine deficiency, D. Riboflavin deficiency
A: Folic acid deficiency
Answer: A: Folic acid deficiency 
Explanation: Folic acid deficiency