Final answer:
The kidneys regulate the volume and composition of plasma and interstitial fluid by filtering blood, controlling electrolytes, and managing the body's pH and osmolarity. The correct answer to the question is option 2) volume : composition.
Step-by-step explanation:
The primary function of the kidneys involves regulating the volume and the composition of plasma and interstitial fluid. The correct answer is option 2) volume : composition. The kidneys maintain homeostasis by controlling the amount of water, ions, and other substances in the blood. They also play a crucial role in osmoregulation, which is the balance of fluids and electrolytes in the body, as well as in regulating blood pressure and the production of certain hormones.
The kidneys function by filtering and secreting metabolites like urea and minerals from the blood, regulating electrolytes such as sodium, potassium, and bicarbonate, and managing the body's pH level and the osmolarity of the blood. Furthermore, they impact the regulation of blood pressure through their control of sodium and water retention and loss. The kidneys' ability to regulate these aspects directly affects the volume and composition of the body's fluids.