Galvanisation is applying a coating of:
A.Cr
B.Cu
C.Zn
D.Pb

Hint: Corrosion is defined as slowly eating away of metal due to the attack of air , water and moisture present in the environment.
When metal is iron in corrosion or we can say that corrosion of iron is called rusting.Rust is apparently a hydrated form of iron(III)oxide. The formula is approximately $Fe_2O_3.32H_2O$, although the exact amount of water is variable.
Rusting can be prevented by galvanization.

Complete step by step answer:
A.Cr – it is used to prevent rusting of iron but the process is not called galvanisation. Hence the option is incorrect.
B.Cu- copper is not used to prevent rusting of iron as itself gets corroded and forms a layer of copper carbonate. So the option is incorrect.
C. Zn – zinc is used to prevent rusting of iron and the process is called galvanization. So the option is exactly correct. It is the process in which a thin layer of zinc metal is deposited on an iron article. It is done by dipping an iron object in molten zinc metal. A thin layer of zinc is then formed all over the iron object. Zinc is used because it does not corrode and is placed above iron in reactivity series. Hence the option is correct.
D.Pb- it is not used to prevent rusting as it is placed low in reactivity series . so this option is incorrect

Our required answer is C that is zinc.


Note:
Zinc is a quite reactive metal. The action of air on zinc metal forms a very thin coating of zinc oxide all over it. This zinc oxide coating is hard and impervious to air and hence prevent the further corrosion of zinc metal the galvanized iron object remain protected against rusting even a break occurs in the zinc layer