Active transport takes place in the absorption of

Nearly all of the essential nutrients,and $70-80\%$ of electrolytes and water are reabsorbed in the

Select the $CORRECT$ statements:
$i$. Tubular secretion involves secretion of $H^{+}$ ions in $PCT$.
$ii$. Augmentation involves secretion of $H^{+}$ ions in $DCT$ and $CT$.
$iii$. Augmentation plays an important role in regulation of $pH$ of blood.
$iv$. Glomerular filtrate as well as urine are acidic.

Which one of the following is mismatched?

Distinct microvilli are present on all of the following except:

Studies of selective reabsorption in humans were conducted by: