Rusting of Iron is catalyzed by:

$H^+$

The correct answer is Option (1) → $H^+$

Rusting of iron is catalyzed by the presence of hydrogen ions (H+), meaning it happens faster in acidic conditions (like acid rain or saltwater) because these ions speed up the electrochemical reactions that form rust (hydrated iron(III) oxide). Water and oxygen are necessary for rusting, but the H+ ions act as the catalyst, facilitating the electron transfer.                  

How it works:  

Anode: Iron loses electrons (\(Fe\rightarrow Fe^{2+}+2e^{-}\)). 

Cathode: Hydrogen ions accept these electrons (\(2H^{+}+2e^{-}\rightarrow H_{2}\)). 

Catalysis: The H+ ions from the acidic environment readily accept the electrons, accelerating the entire process and leading to faster corrosion.