B Suffered a Loss of Dopamine-Secreting Neurons in His Brain

B. suffered a loss of dopamine-secreting neurons in his brain after ingesting a neurotoxin. Which of the therapies below was successful in restoring his motor function?

A) injection of fetal nigrostriatal neurons into Mr. B.'s caudate nucleus and putamen
B) oral ingestion of L-DOPA
C) oral ingestion of cocaine and amphetamine
D) infusion of dopamine directly into Mr. B.'s caudate nucleus and putamen
E) injection of radioactive L-DOPA