Final answer:
In renal compensation for respiratory acidosis, the urine pH decreases due to increased secretion of H+, which assists in restoring blood pH balance. Therefore, the answer to the student's question is b. decreased because [H+] increased."
Step-by-step explanation:
When considering renal compensation for respiratory acidosis, an increased secretion of H+ ions into the urine and an increased reabsorption of bicarbonate (HCO3-) into the blood occurs. In renal compensation for respiratory acidosis, the urine pH decreases due to increased secretion of H+, which assists in restoring blood pH balance.
This process helps to reestablish the proper balance between bicarbonate and carbonic acid, thereby correcting the blood pH. As a result, the pH of the urine decreases because H+ concentration increases, as the kidneys try to conserve bicarbonate and secrete more H+ to combat the acidity.
Therefore, the answer to the student's question is: "With renal compensation for respiratory acidosis, the pH of the urine b. decreased because [H+] increased."