Chemical changes:
Chemical changes occur when the composition and properties of a substance are altered to form a new substance with different properties. In chemical changes, new chemical bonds are formed or existing bonds are broken. Let's analyze each option to determine which of them involve chemical changes.

A: Freezing of water
Freezing is a physical change, not a chemical change. It is a process in which a substance changes from a liquid state to a solid state due to a decrease in temperature. In this case, water molecules rearrange themselves into a rigid, crystalline structure without any change in their chemical composition.

B: Cooking of vegetables
Cooking of vegetables involves various chemical changes. When vegetables are cooked, several chemical reactions occur, leading to changes in their composition and properties. Some of these changes include:

- Denaturation of proteins: Heat causes the proteins in vegetables to unfold and lose their original structure, resulting in changes in texture and taste.
- Caramelization: Sugars present in vegetables undergo thermal decomposition and react with each other, forming new compounds that contribute to the browning and flavor development.
- Maillard reaction: A complex chemical reaction occurs between amino acids and reducing sugars at high temperatures, resulting in the browning and development of desirable flavors.
- Decomposition of vitamins: Cooking can lead to the breakdown of certain heat-sensitive vitamins, reducing their nutritional value.

C: Drying of wet clothes in sunlight
Drying of wet clothes in sunlight is also a physical change. It involves the evaporation of water from the clothes due to the heat and energy provided by sunlight. The water molecules change from a liquid state to a gaseous state without any alteration in their chemical composition.

D: Melting of ice
Melting is another example of a physical change. Ice melts when heat is added, causing the water molecules to gain enough energy to overcome the attractive forces holding them together in a solid lattice. The result is a transition from a solid state to a liquid state, but the chemical composition of water remains the same.

Conclusion:
Among the given options, only the cooking of vegetables (option B) involves chemical changes. The other options (A, C, and D) are examples of physical changes.