Physical changes involve a change in the state or form of a substance without altering its chemical composition. In other words, the substance remains the same at the molecular level. Among the given options, the physical change is:

b) Cooking of food

Explanation:

Cooking food is a physical change because it involves the application of heat, which causes a change in the state or form of the food without altering its chemical composition. Here is a detailed explanation:

1. Change in State: When food is cooked, it undergoes a change in state. For example, raw vegetables become softer and more tender when cooked. This change in texture is due to the heat breaking down the cell walls in the vegetables, making them easier to chew and digest.

2. Change in Appearance: Cooking also causes a change in the appearance of food. Raw meat, for instance, turns from pink or red to brown when cooked. This change in color is due to the heat-induced chemical reactions that occur in the proteins of the meat.

3. No New Substances Formed: Despite the changes in state and appearance, the chemical composition of the food remains the same. The molecules and atoms that make up the food do not undergo any chemical reactions or rearrangements during the cooking process.

4. Reversible Change: Physical changes, such as cooking, are usually reversible. If we were to cool down the cooked food, it would return to its original state, although its texture might be slightly altered.

Other options:

a) Rusting of iron: Rusting of iron is a chemical change because it involves the reaction of iron with oxygen in the presence of moisture, leading to the formation of iron oxide (rust). This change is irreversible and results in the formation of a new substance.

c) Evaporation of water: Evaporation of water is a physical change because it involves the change of water from its liquid state to a gaseous state (water vapor) due to the application of heat. The chemical composition of water remains the same during evaporation.

d) Rotting of fruits: Rotting of fruits is a chemical change because it involves the breakdown of organic compounds in the fruit by microorganisms, such as bacteria or fungi. This decomposition process leads to the formation of new substances and the release of unpleasant odors.