The diagram below shows the structure of a single nephron.

Complete the table below by matching the correct letter or letters (AAA, BBB, CCC, or DDD) of the nephron to each statement.
| Statement | Letter(s) |
|---|---|
| Active reabsorption of all filtered glucose and amino acids occurs here | |
| Permeability to water is increased by the action of antidiuretic hormone (ADH) | |
| Ultrafiltration occurs here due to high hydrostatic pressure |
Outline the physiological processes occurring in the ascending and descending limbs of the loop of Henle that establish the concentration gradient shown by the downward-pointing arrow.