Answer B. Two
According to 2018 guidelines from the International Ketogenic Diet Study Group, ketogenic diets should be considered in children after two failed trials of antiepileptic drugs. Earlier initiation can be considered in children with certain epilepsy syndromes, such as Angelman Syndrome, infantile spasms, or FIRES.
Source: Kossoff EH, Zupec-Kania BA, Auvin S, et al, for the Practice Committee of the Child Neurology Society. Optimal clinical management of children receiving dietary therapies for epilepsy: Updated recommendations of the International Ketogenic Diet Study Group. Epilepsia Open. 2018;3:175-192.