Which one of the following statements is not correct? A. Over a week-long period, if a healthy person were to ingest 35 g of NaCl, the total amount of NaCl excreted in the urine would be less than 35 g. B. In the proximal tubule, large amounts of Na + and water are reabsorbed but the concentration of Na + in the proximal tubular fluid does not change. C. A drug that inhibits active NaCl reabsorption in the ascending limb of the loop of Henle will likely increase the volume of urine production. D. If a substance is present in the urine, that substance must necessarily be filtered out of the glomerulus into Bowman's capsule. E. Fluid in the proximal tubule does not normally contain protein.

The option D is incorrect.

Explanation:

It is not necessary that the substance needs to get filtered out of the glomerulus to be present within the urine. Some of the substances may be present in the urine due to the secretion in the renal tubules post the filtration process in the glomerulus.

Like in the proximal tubule of the nephron, secretion results in the transport of some of the molecules out of the blood and within the urine. These secreted substances can be hydrogen ions, potassium ions, creatinine ions, and some kinds of waste components like drugs.

The conduction of substances from peritubular capillaries to the renal tubular lumen is termed as tubular secretion, and the process generally takes place by passive diffusion and active transport.