Statement A: In the descending limb of loop of Henle, the urine is hypertonic, whereas in ascending limb of loop of Henle, the urine is hypotonic.
Statement B: Descending limb is impermeable to sodium, while ascending limb is impermeable to water.

Descending limb of loop of Henle is permeable to water but not to sodium. Consequently water moves out into interstitium and concentration of sodium in tubular filtrate rises making filtrate hypertonic. Ascending limb of loop of Henle is impermeable to water but permeable to sodium and makes the filtrate hypotonic.