Which of the following is a combustible substance ?

Options

A. Cement
B. Glass
C. Stone
D. Cow -dung cake

Answer

To determine which of the given substances is a combustible substance, we need to analyze each option based on its ability to undergo combustion (burning).

### Step-by-Step Solution:

1. **Identify the Options**: The options given are:
- Cement
- Glass
- Stone
- Cow dung cake

2. **Analyze Each Option**:
- **Cement**: Cement is primarily used in construction. It is a mixture of various compounds and does not burn. Therefore, cement is not a combustible substance.
- **Glass**: Glass is made from silica and has a very high melting point. It does not burn or undergo combustion. Thus, glass is not a combustible substance.
- **Stone**: Stones are solid minerals that are also used in construction. They are very hard and do not burn. Therefore, stones are not combustible.
- **Cow Dung Cake**: Cow dung cake is a by-product of livestock and is often used as a fuel in rural areas. It can burn and release heat when ignited, making it a combustible substance.

3. **Conclusion**: Among the options provided, the only combustible substance is **Cow Dung Cake**.

### Final Answer:
Cow dung cake is a combustible substance.

---