Catalysis

Step 1: Identifying the rusting process.
Rusting of iron involves both electrochemical reactions and the presence of an electrolyte. The presence of oxygen (O ) and moisture facilitates the process, but hydrogen ions (H ) catalyse the rusting by lowering the potential for the oxidation of iron.

Step 2: Understanding the role of H .
- (1) Fe: Iron itself is not a catalyst; it is the metal undergoing oxidation.
- (2) Zn: Zinc does not catalyse rusting; in fact, it is often used to protect iron through galvanization.
- (3) O : While oxygen is necessary for rusting, it is not the catalyst.
- (4) H : Hydrogen ions (acidic conditions) help in the corrosion process by facilitating the transfer of electrons during oxidation.

Step 3: Conclusion.
The correct answer is (4) H .

Step 1: Formula / Definition}

Step 2: Calculation / Simplification}
Aryl alkyl ethers react with HI to give phenol and alkyl iodide.
The cleavage occurs at the alkyl-oxygen bond, forming phenol as the main organic product along with alkyl iodide.
Thus, the product corresponds to option (b).
Step 3: Final Answer