Which of the following organs regulates the levels of water, salts , hydrogen ions and urea in the mammalian blood?

The organ that regulates the levels of water, salts, hydrogen ions, and urea in the mammalian blood is the Kidney. The kidney is an important organ responsible for filtering the blood and removing waste products such as urea, excess salts, and hydrogen ions. It also regulates the amount of water in the body by either retaining it or excreting it in the urine, depending on the body's needs. The kidneys work by filtering blood through tiny structures called nephrons, which remove waste products and excess fluids from the blood. The filtered blood is then returned to circulation, while the waste products are excreted as urine. The kidney also plays a crucial role in maintaining the body's acid-base balance by regulating the levels of hydrogen ions in the blood. If the blood becomes too acidic or too alkaline, the kidneys adjust the levels of hydrogen ions in the blood to bring it back into balance. In summary, the kidney is the organ that regulates the levels of water, salts, hydrogen ions, and urea in the mammalian blood by filtering the blood, removing waste products, and regulating the amount of water in the body.