The Digestive, Respiratory, and Urinary Systems Are Similar in That

The digestive, respiratory, and urinary systems are similar in that they all help maintain

A) fluid level in the blood.
B) constant temperature in the body.
C) balance of substances in the blood.
D) oxygen levels in the blood.
E) control of the other body systems. The only answer that applies to all three systems is balance of substances in the blood. The digestive system influences nutrient levels; the respiratory system maintains oxygen and carbon dioxide levels; the urinary system rids the blood of wastes.