The correct answer is option C - Oxidation of the rust.

Although rust (iron(III) oxide) is a base and can react with sulfuric acid, the primary reason sulfuric acid is effective in removing rust is that it oxidizes the rust, breaking it down into soluble iron(III) sulfate.

However, it's worth noting that option B, "Reaction of acid with base", is also a correct description of the reaction. But the question asks for the type of reaction that makes the removal of rust possible, and oxidation is the key process in this case.