Which organ system eliminates waste and regulates water balance?

• A. Digestive system
• B. Circulatory system
• C. Urinary (excretory) system
• D. Nervous system

Answer: (C)

Waste elimination and water balance are handled by the urinary (excretory) system. The kidneys filter waste from the blood and regulate fluid and electrolyte levels, adjusting urine production to maintain proper hydration, osmolarity, and pH. Urine, containing the waste products and excess ions, is then expelled from the body via the urinary tract. This combination of removing waste and actively managing water balance is why this system is the best fit for the question.

Other systems don’t perform both tasks together: the digestive system mainly eliminates solid waste, not regulating body water balance; the circulatory system transports wastes and nutrients but does not excrete them; the nervous system helps regulate many processes, but it isn’t the organ system that directly eliminates waste or controls water balance.