Which of the following are oxidation reactions?

I. Rusting of iron
II. Burning of fuel
III. Rancidity of oils and fats
IV. Browning of fruits

Select the correct answer using the code given below.

All four processes listed are examples of oxidation reactions occurring in daily life:

• Rusting of iron: Iron reacts with oxygen and moisture to form hydrated iron(III) oxide (Fe2O3·nH2O). This is a slow oxidation process.
• Burning of fuel: Combustion is a rapid chemical reaction where a substance reacts with oxygen to release heat and light.
• Rancidity: This occurs when fats and oils in food are oxidized, leading to the development of a foul smell and taste.
• Browning of fruits: When fruits like apples are cut, the enzyme polyphenol oxidase reacts with atmospheric oxygen to produce brown pigments (melanins), an enzymatic oxidation process.

Since all these processes involve the addition of oxygen or the loss of electrons, they are all oxidation reactions.