Galvanized iron sheets are coated with:

Galvanization is the process of securing a protective coating to the surface of iron or steel in order to safeguard it. The layer guards against corrosion on the material's surface. due to the material's surface potentially being harmed by the interaction with atmospheric chemicals.

Zinc is utilised as a coating to shield the steel or iron surface. The zinc coating functions as a protective shield between the iron and the corrosive substances that cause oxidation and iron rust. when a piece of galvanised metal comes into touch with the environment and dangerous substances. Iron does not oxidise because of the coating of zinc that is present on the surface of the substance.

In comparison to iron, zinc is more reactive. When a surface that has been galvanised oxidises, the zinc that is already there combines with air and water to coat the iron with a protective coating of zinc oxide.
Zinc continually breaks down and interacts with its environment to stop iron from rusting. Long-term protection from iron is provided by zinc, and if the galvanization fails, the reactive element zinc interacts with iron to stop the inner layers of iron from rusting.
Galvanization, then, is the application of a zinc coating.

Hence, the correct answer is C.