Human urine as compared to human blood is

Compare the statements $A$ and $B$.
$\text{Statement } A$: When the urine moves through the descending limb,it becomes hypertonic,and as it passes through the ascending limb of Henle's loop,it becomes hypotonic.
$\text{Statement } B$: The descending limb is permeable to sodium ions,while the ascending limb is impermeable to sodium ions.

Indicate whether the following statement is true or false:
Henle's loop plays an important role in concentrating the urine.

Salmon have gills that are more permeable to water than to salts. Salmon hatch in fresh water streams and then migrate to the ocean. Once they reach the ocean,you would expect the rate of uptake of water into their body through the gills to:

Describe the counter-current mechanism.

What is the osmolarity of the filtrate at the hairpin bend of the loop of Henle?