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
Gum hypertrophy is an adverse effect of the following drug when used at therapeutic levels : 
Select and explain. 
A. Phenobarbitone, B. Phenytoin, C. Carbamazepine, D. Sodium valproate
B: Phenytoin
Answer: B: Phenytoin 
Explanation: None