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
A young male, Farhan suffers from a seizure disorder which is characterized by tonic rigidity of limbs followed in 20-30 sec by tremors progressing to massive jerking of the body. This clonic phase lasts for 1–3 min. The anti–seizure drug of choice for this patient is : 
Select and explain. 
A. Clonazepam, B. Ethosuximide, C. Fosphenytoin, D. Valproic acid
D: Valproic acid
Answer: D: Valproic acid 
Explanation: None