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 :
Clonazepam
Ethosuximide
Fosphenytoin
Valproic acid