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
In  a  healthy  individual  on  a  normal  diet,  which of  the  following  ion is  completely  absorbed  in  tubules? 
Select and explain. 
A. Na +, B. K, C. Cl –, D. HCO3 –
D: HCO3 –
Answer: D: HCO3 – 
Explanation: None