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 patient of Parkinsonism is managed with levodopa. If Vitamin B complex is administered concurrently to the patient : 
Select and explain. 
A. The action of levodopa in brain will be potentiated, B. Decarboxylation of 1–dopa in brain will be decreased, C. Side effects will be ameliorated, D. Decreased efficacy will result
D: Decreased efficacy will result
Answer: D: Decreased efficacy will result 
Explanation: None