Which of the following is not biotic factor?

Options

A. Plants
B. Animals
C. Microorganisms
D. Stones

Explanation

To determine which of the following is not a biotic factor, we need to understand the definitions of biotic and abiotic factors.

### Step-by-Step Solution:

1. **Define Biotic Factors**: Biotic factors are all living components of an ecosystem. This includes plants, animals, and microorganisms. These factors interact with each other and with their environment.

2. **Define Abiotic Factors**: Abiotic factors are non-living components of an ecosystem. This includes elements like water, air, soil, temperature, and rocks. These factors influence the living organisms in an ecosystem but do not consist of living entities themselves.

3. **Analyze the Options**:
- **Option 1: Plant** - Plants are living organisms, so they are biotic factors.
- **Option 2: Animal** - Animals are also living organisms, making them biotic factors.
- **Option 3: Microorganism** - Microorganisms, such as bacteria and fungi, are living entities, thus they are biotic factors.
- **Option 4: Stone** - Stones are non-living components of the ecosystem, so they are abiotic factors.

4. **Conclusion**: Among the options provided, the stone is not a biotic factor. Therefore, the correct answer is the fourth option.

### Final Answer:
The option that is not a biotic factor is **stone**.