Let’s take a look at each assertion separately.
(a) Water is impermeable to the ascending limb of Henle’s loop but permeable to the descending limb.
An ascending limb, a descending limb, and a hairpin constitute Henle’s loop. The descending limb of the Henle loop is permeable to water but not to electrolytes. This concentrates the filtrate as water moves out of the limb as the filtrate descends. The filtrate is diluted as it goes upward because the ascending limb is impermeable to water but permeable to electrolytes.

(b)The hormones vasopressin and antidiuretic hormone aid in the reabsorption of water from the tubules’ distal regions (ADH).
The hypothalamus produces vasopressin, which is released by the posterior pituitary. The process of urine generation is known as diuresis, and vasopressin prevents urine formation by reducing water loss through urine by increasing water absorption from later portions of the tubules. As a result, it’s also known as the antidiuretic hormone.

(c)With the exception of nitrogenous wastes, dialysis fluid contains all of the constituents found in plasma.
Haemodialysis is the process of purifying blood with an artificial kidney when the natural kidney is no longer capable of doing so. The blood is pumped into a dialyzing unit, which contains a fluid that has all of the ingredients found in plasma except nitrogenous wastes; as a result, the nitrogenous wastes flow from the blood into the dialyzing fluid according to the concentration gradient.

(d)A healthy adult individual excretes 25-30 grams of urea every day on average.
An adult human excretes about 1-1.5 liters of urine every day on average.