What should be used to fill up battery fluid and how much?

Answer: B — Distilled water, just above the cell plates

Distilled water should be used to fill up battery fluid, just above the cell plates. Tap water contains minerals and impurities that can damage the battery. Engine oil should never be used as it is not compatible with the battery's chemical composition. Filling the battery fluid to the very top of the cell plates can cause overflow and damage the battery. It is important to only fill the fluid just above the cell plates to allow room for expansion.