Which of the following is NOT listed as a function of water in the animal's body?

• A. Eliminate waste products of digestion and metabolism
• B. Regulate blood osmotic pressure
• C. Produce milk and saliva
• D. Fight infections

Answer: (D)

Water in the body mainly serves as a solvent and transport medium. It dissolves nutrients and wastes and helps carry them to sites of metabolism or excretion, so eliminating waste products of digestion and metabolism depends on adequate water. It also helps regulate osmotic pressure, keeping fluid balance across membranes and supporting proper blood volume and tissue hydration.

Water is the major component of secretions like saliva and milk, so its presence is necessary for the production of these fluids—the glands rely on ample water to secrete.

Fighting infections is primarily the job of the immune system. Water supports hydration and circulation, which aid overall health, but it does not directly perform immune responses; its role is supportive rather than a primary function.