The correct answer is option 2, Lead, which is used in storage batteries.

Storage batteries, also known as rechargeable batteries, are used to store electrical energy and release it when needed. Lead is commonly used in these batteries for its unique properties.

Lead-acid batteries, the most common type of storage battery, have lead as one of the main components. These batteries are widely used in vehicles, backup power systems, and other applications.

Lead is chosen for storage batteries because of its high density, which allows for efficient energy storage. It also has good corrosion resistance and can withstand the chemical reactions that occur during the charging and discharging process.

While other metals like copper, tin, and zinc can be used in various applications, they are not commonly used in storage batteries. Copper is a good conductor of electricity and is often used in electrical wiring and circuits. Tin is used in soldering and plating, while zinc is commonly used in galvanizing and as a sacrificial anode for corrosion protection.

In conclusion, lead is the correct option because it is the primary metal used in storage batteries due to its beneficial properties for efficient energy storage and durability.