Final answer:
The secretion of hydrogen ions into the renal tubule is true and crucial for regulating body fluid acidity. The kidneys do this by secreting H+ into the urine, which helps maintain the pH of blood.
Step-by-step explanation:
The statement that the secretion of hydrogen ions into the renal tubule helps regulate the acidity of body fluids is True. Specifically, in the distal tubule of the nephron and the early part of the collecting duct, the kidneys contribute to acid-base balance by actively secreting excess hydrogen ions (H+) into the urine. This lowers the plasma's acidity and increases urine acidity, effectively removing H+ from the bloodstream to maintain the pH within a narrow and healthy range. Intercalated cells are particularly significant in this process, using proton pumps on their apical surfaces to move H+ into the urine. Thus, in conjunction with the lungs, the kidneys play a crucial role in regulating the body's overall acid-base balance.