RRB Group D Model Paper 4 with solutions

(2) Rusting of iron occurs in the presence of oxygen and water. Rust is the oxidized form of iron. Iron rusts because it combines with oxygen. The oxygen needs moisture as a catalyst and reactant to accelerate the reaction, so in the absence of moisture, iron won't rust. So the thing that causes iron to rust is the presence of water or moisture from which the iron can take the oxygen it wants