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
[{'content': "Which of the following is a 'nootropic' drug \nSelect and explain. \nA. Rivastigmine, B. Tacrine, C. Amantadine, D. Piracetam", 'role': 'user'}, {'content': 'Answer: D \nExplanation: Nootropic drugs are those that enhance memory. Piracetam is used for this function in patients with head injury.', 'role': 'assistant'}]