C. Building can be protected by using a lightning rod at the top of the building.

Explanation:
- Benjamin Franklin's discovery of using a lightning rod to protect buildings from lightning strikes is one of his most significant contributions to science and technology.
- Franklin conducted experiments and made observations to understand the nature of lightning and how it could be harnessed and controlled.
- He hypothesized that lightning is a form of electricity and that it can be directed away from buildings by providing a conductive path for it to follow.
- Franklin designed and installed lightning rods on buildings, which are metal rods placed at the highest point of a structure and connected to the ground.
- The lightning rod acts as a lightning attractor, providing a path of least resistance for the lightning to follow and safely guiding it into the ground.
- By diverting the electrical charge away from the building, the lightning rod helps to prevent damage from lightning strikes, such as fires and structural damage.
- Franklin's invention of the lightning rod revolutionized the protection of buildings and has since been widely adopted around the world.
- It not only saved countless lives and properties but also paved the way for further advancements in electrical engineering and the understanding of electricity.
- Franklin's work on lightning rods also led to the development of other lightning protection systems and devices, such as surge protectors and grounding systems.
- Today, lightning rods are a common sight on tall structures, residential buildings, and historical landmarks, ensuring their safety during thunderstorms.
- Franklin's discovery and innovation in lightning protection continue to have a lasting impact on modern society, making him a pioneer in the field of electrical safety.