Explanation: The Edison-type storage cell (nickel-iron battery) utilizes an alkaline electrolyte. * **C) Is a 21% solution of potassium and lithium hydroxides in distilled water:** This accurately describes the chemical composition of the electrolyte. Potassium hydroxide (KOH) provides conductivity, and lithium hydroxide (LiOH) improves charge acceptance and capacity. * **B) Has a specific gravity of about 1.200:** This is the typical specific gravity of the alkaline electrolyte in an Edison cell. A key characteristic is that, unlike lead-acid batteries, the specific gravity of the electrolyte in an Edison cell does *not* significantly change with the state of charge, as the electrolyte does not actively participate in the chemical reaction. * **A) Is contained in a nickel-plated sheet steel tank:** Edison cells are known for their robust and durable construction. The electrolyte is housed in sturdy, nickel-plated sheet steel containers to withstand the corrosive alkaline solution and mechanical stress. Since statements A, B, and C are all correct descriptions pertaining to the electrolyte and construction of an Edison-type storage cell, **D) All of the above** is the correct answer.