Option 1: The statement that rusting of an iron nail decreases its weight is incorrect. Rusting is an oxidation process that occurs when iron reacts with oxygen in the presence of water or moisture. During this process, iron combines with oxygen to form iron oxide, which is commonly known as rust. The formation of rust on the surface of the iron nail actually increases its weight. Consequently, option 1 is incorrect.

Option 2: This is the correct answer. The rusting of an iron nail increases its weight. As the iron reacts with oxygen in the presence of water, it combines with the oxygen to form iron oxide (rust). The iron oxide adds additional mass to the nail, making it heavier than it was before the rusting process took place.

Option 3: This option correctly states that rusting does not affect the weight of the iron nail. However, it is important to note that rusting is caused by the oxidation of iron, which means that iron is being oxidized during the process. So, while the weight of the nail may remain the same, iron is indeed being oxidized.

Option 4: This option is incorrect. Rusting does not involve the reduction of iron. Rather, it involves the oxidation of iron as it reacts with oxygen