Explanation: Lead-acid batteries require distilled water because water naturally evaporates from the electrolyte (a solution of sulfuric acid and water), especially during the charging process. Keeping the electrolyte level about 1/4 inch above the top of the plates (A) is crucial. If the plates are exposed to air, they can dry out, sulfate, and become permanently damaged or inactive. This directly impacts the battery's performance by reducing the useful plate area (B) available for the electrochemical reaction. A diminished active plate area means the battery cannot maintain its full current capacity, severely degrading its overall performance and lifespan. Using distilled water prevents the introduction of minerals and impurities that could harm the battery's chemistry.