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': 'The dose of a drug required to produce a specified effect in 50% of the population is \nSelect and explain. \nA. Ld50, B. Td50, C. Md50, D. Ed50', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]