This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Excretory System, Subject name: Physiology
If a patient has a creatinine clearance of 90 ml/min, a urine flow rate of 1 ml/min, a plasma K+ concentration of 4 mEq/L, and a urine K+ concentration of 60 mEq/L, what is the approximate rate of K+ excretion? 
Select and explain. 
A. 0.06 mEq/min, B. 0.30 mEq/min, C. 0.36 mEq/min, D. 3.6 mEq/min
A: 0.06 mEq/min
Answer: A: 0.06 mEq/min 
Explanation: K+ excretion rate = (urine K+ concentration) x (urine flow rate) = (60 mEq/L) x (0.001 L/min) = 0.06 mEq/ min.