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
High plasma drug concentration of phenytoin can cause which of the following adverse effects ? 
Select and explain. 
A. Ataxia, B. Hirsutism, C. Gum hyperplasia, D. All of the above
A: Ataxia
Answer: A: Ataxia 
Explanation: None