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: Physiology
If clearance of a drug equals the CFR, it implies that 
Select and explain. 
A. Drug is reabsorbed in renal tubules, B. Drug is secreted into renal tubules, C. Drug is neither secreted or reabsorbed in renal tubules, D. None of the above
B: Drug is secreted into renal tubules
Answer: B: Drug is secreted into renal tubules 
Explanation: Clearance = GFR, If there is no secretion or reabsorption in renal tubules.
Clearance > GFR, there is net tubular secretion.
Clearance < GFR, there is net tubular reabsoption.