The example for exothermic reaction is

Options

A. melting of ice cubes
B. decomposition of vegetable matter into compost
C. cooking an egg
D. baking bread.

Explanation

**Step-by-Step Solution:**

1. **Understanding Exothermic Reactions:**
- An exothermic reaction is defined as a chemical reaction that releases energy in the form of heat or light. In these reactions, the energy of the products is lower than that of the reactants.

2. **Analyzing the Given Options:**
- We need to evaluate each option provided to determine which one represents an exothermic reaction.

3. **Option A: Melting of Ice Cubes**
- The melting of ice is a process that requires energy from the surroundings to convert solid ice into liquid water. Therefore, this process absorbs energy and is classified as an endothermic reaction.

4. **Option B: Decomposition of Vegetable Matter into Compost**
- The decomposition of vegetable matter involves microbial activity that breaks down organic material. While the initial breakdown requires energy (making it endothermic), the overall process releases energy as compost is formed. Thus, the net energy change is exothermic.

5. **Option C: Cooking an Egg**
- Cooking an egg requires heat to denature the proteins present in the egg. This process consumes energy, making it an endothermic reaction.

6. **Option D: Baking Bread**
- Similar to cooking an egg, baking bread requires heat to cause the dough to rise and cook. This process also consumes energy, classifying it as an endothermic reaction.

7. **Conclusion:**
- After analyzing all the options, the only process that can be classified as exothermic is the decomposition of vegetable matter into compost (Option B).

**Final Answer:**
The example of an exothermic reaction is **Option B: Decomposition of vegetable matter into compost.**

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