What is the primary function of the kidneys?

• A. Filter waste, regulate fluids and electrolytes, and maintain acid-base balance
• B. Produce insulin to regulate blood sugar
• C. Store minerals for bone health
• D. Pump blood through the body

Answer: (A)

The kidneys are mainly responsible for keeping the body's internal environment stable by filtering the blood to remove waste and excess fluids, and by finely tuning electrolyte levels and acid-base balance. They filter plasma through nephrons, reabsorb what the body needs, and excrete wastes and excess minerals into urine, adjusting fluid volume and composition as needed. They also maintain pH by regulating bicarbonate and hydrogen ion levels, helping keep blood acidity in a narrow, healthy range. While they do other important jobs (like helping control blood pressure and producing hormones), the primary function described is waste removal alongside fluid, electrolyte, and acid-base regulation. Other choices point to different organs: insulin production is from the pancreas, mineral storage is a bone function, and pumping blood is the role of the heart.