The regulatory system of acid-base balance takes the longest time to respond, and regulates the pH of extracellular fluid (ECF) by eliminating hydrogen ions or bicarbonate in body fluids?

Rationale: A. The respiratory system responds within minutes by altering CO₂ levels through breathing, but it is not the slowest system. B. Chemical buffer systems act immediately to maintain pH balance but are only a temporary solution. C. The endocrine system plays a role in general homeostasis but is not a primary regulator of acid-base balance. D. The renal system is the slowest but most powerful regulator of acid-base balance. It maintains long-term pH stability by excreting hydrogen ions and reabsorbing bicarbonate.