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': 'A drug given at the loading dose of 20mg reaches plasma concentration of  0.5mg/L, If apparent volume of distribution is 40L, Calculate Bio availability of the drug \nSelect and explain. \nA. 70%, B. 80%, C. 90%, D. 100%', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]