Renal Physiologists Are Investigating How Hydration Status Affects Human Urine

Renal physiologists are investigating how hydration status affects human urine concentration and dilution mechanisms. To accomplish this, they developed a technique in experimental animals that allows tubular fluid sampling in various parts of the nephron. After 12 hours of water deprivation, a healthy animal produces a tubular fluid sample with an osmolarity of 110 mOsm/L. If the physiology of this animal is similar to that of humans, which of the following sites along the nephron was most likely sampled?

A) A
B) B
C) C
D) D
E) E