Which one of the following statements is correct? A: Chlorpromazine is indicated in treating the nausea of levodopa treatment. B: Vitamin B6 increases the effectiveness of levodopa. C: Administration of dopamine is an effective treatment of Parkinson’s disease. D: Levodopa-induced nausea is reduced by carbidopa. E: Nonspecific MAO-inhibitors, such as phenelzine, are a useful adjunct to levodopa therapy.