Final answer:
All of the above mechanisms—buffering, respirations, and urine secretion—are necessary for the body to maintain acid-base balance. So the correct answer is option (D).
Step-by-step explanation:
For the body to maintain an acid-base balance, it is necessary to have the synchronized function of multiple systems. These include buffering mechanisms, respirations (ventilation), and urine secretion. Each of these components plays a crucial role:
Buffering mechanisms involve the use of substances like bicarbonate and proteins, which can quickly absorb or release hydrogen ions to maintain pH levels.
Respirations adjust the levels of carbon dioxide in the blood, which can in turn modify the pH due to their role in forming carbonic acid.
Urine secretion allows the kidneys to excrete excess hydrogen ions and reabsorb bicarbonate, thus having a lasting impact on the acid-base balance.
Therefore, the correct answer to the option is d. All the above are necessary to maintain an acid-base balance within the optimal pH range for physiological function, which is typically between 7.35 and 7.45.