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': 'Complete drug elimination occurs after how many hours, if t½ is 4 hrs.: \nSelect and explain. \nA. 12 hrs., B. 20 hrs., C. 25 hrs., D. 30 hrs.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]