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: Medicine
[{'content': 'Drug used to halt process of degeneration of dopaminegric neurons in nigrostrial pathway is - \nSelect and explain. \nA. Vit E, B. Vit A, C. Propranolol, D. Levodopa', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]