The correct answer is A. silver oxide.
Silver oxide is the active material of the positive plates of silver-zinc batteries. It is a black powder that is mixed with a binder and then pressed into a plate. When the battery is discharged, the silver oxide reacts with zinc to produce silver metal and zinc oxide. The reverse reaction occurs when the battery is charged.
Lead oxide is the active material of the positive plates of lead-acid batteries. It is a red powder that is mixed with a binder and then pressed into a plate. When the battery is discharged, the lead oxide reacts with sulfuric acid to produce lead sulfate and water. The reverse reaction occurs when the battery is charged.
Lead is the active material of the negative plates of lead-acid batteries. It is a gray metal that is cast into a plate. When the battery is discharged, the lead reacts with sulfuric acid to produce lead sulfate and water. The reverse reaction occurs when the battery is charged.
Zinc powder is the active material of the negative plates of zinc-carbon batteries. It is a white powder that is mixed with a binder and then pressed into a plate. When the battery is discharged, the zinc reacts with manganese dioxide to produce zinc oxide and manganese dioxide. The reverse reaction occurs when the battery is charged.