The Loop of Henle is primarily responsible for the reabsorption of which of the following?

If Henle's loop were absent from mammalian nephron,which of the following is to be expected?

At the bottom of the loop of Henle,the glomerular filtrate is . . . . . . .

Which one of the following animals has a longer loop of Henle?

Which of the following plays a significant role in the production of concentrated urine?

The increase in osmolarity from outer to inner medullary interstitium is maintained due to:
$(i)$ Close proximity between Henle's loop and vasa recta
$(ii)$ Counter current mechanism
$(iii)$ Selective secretion of $HCO_{3}^{-}$ and hydrogen ions in $PCT$
$(iv)$ Higher blood pressure in glomerular capillaries