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
Where in the kidney does active reabsorption of sodium ions occur 
Select and explain. 
A. Collecting duct, B. Distal tubule, C. Ascending limb of Henle, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Other than at thin descending limb of the loop of Henle, all other sites of tubule Na+ are reabsorbed by various mechanisms.
-        Proximal tubule- 60-70%

Na+- H+ exchange
Na+- Glucose co-transport
Na+- amino acid co-transport
Na+ unitransport

-        The thick ascending limb of the loop of Henle - 30%

Na+- 2Cl-- K+ co-transport

-        Early distal tubule- 7%

Na+- Cl- co-transport

-        Late distal tubule and collecting duct - 3%

ENaC channels