What is the counter current mechanism?

Given below are two statements with respect to counter current mechanism.
$Statement-I$: Tissue fluid around the descending limb of Henle's loop becomes concentrated, during the counter current mechanism.
$Statement-II$: Water moves out from the descending limb of Henle's loop into the tissue fluid by osmosis.
In the light of the above statements, select the correct option from the codes given below:

The main function of Henle's loop is

If the $Loop$ $of$ $Henle$ is absent from the mammalian nephron,which of the following is likely to occur?

What is the range of osmolarity from the renal cortex to the inner medulla?

Select the correct option:
$(1)$ The counter-current mechanism is maintained by the Loop of Henle and the vasa recta.
$(2)$ The ascending limb of the Loop of Henle is impermeable to water.