In which process is a protective zinc coating applied on iron to prevent it from rusting?

Galvanization

The correct answer is option 3. Galvanization.

The process in which a protective zinc coating is applied on iron to prevent it from rusting is Galvanization

Galvanization involves the application of a layer of zinc onto the surface of iron or steel to protect it from corrosion. This process forms a barrier between the iron/steel and the surrounding environment, preventing the iron/steel from coming into direct contact with oxygen and moisture, which are the primary causes of rusting.