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
Loading dose of 25mg was needed to achieve 0.5mg / L of Plasma concentration. Volume of distribution is 40L. Calculate the Bioavailabity 
Select and explain. 
A. 40%, B. 50%, C. 80%, D. 70%
C: 80%
Answer: C: 80% 
Explanation: None