Which of the following is not a use of micro- organisms?

Options

A. Preparation of medicines ( or drugs)
B. preparation of food by photosynthesis
C. Recycling of materials in nature
D. increasing the fertility of soil.

Answer

To determine which of the following is not a use of micro-organisms, we will analyze each option provided.

### Step-by-Step Solution:

1. **Identify the Uses of Micro-organisms**:
- Micro-organisms are known to be involved in various processes, including the preparation of medicines, recycling of materials, and increasing soil fertility.

2. **Option Analysis**:
- **Option 1: Preparation of Medicines or Drugs**:
- Micro-organisms such as *Penicillium* (which produces penicillin) and *Streptomyces* (which produces streptomycin) are indeed used in the production of antibiotics and other drugs. Therefore, this is a valid use of micro-organisms.

- **Option 2: Preparation of Food by Photosynthesis**:
- Photosynthesis is a process that primarily involves plants, which use sunlight and chlorophyll to convert carbon dioxide and water into glucose and oxygen. Micro-organisms are not involved in this process, making this option a correct answer to the question as it is not a use of micro-organisms.

- **Option 3: Recycling of Materials in Nature**:
- Micro-organisms play a crucial role in decomposition and recycling of nutrients in ecosystems. They break down complex organic materials into simpler substances, thus aiding in nutrient cycling. This is a valid use of micro-organisms.

- **Option 4: Increased Soil Fertility**:
- Certain bacteria, such as *Rhizobium*, are known to fix atmospheric nitrogen, enriching the soil and increasing its fertility. This is also a valid use of micro-organisms.

3. **Conclusion**:
- After analyzing all options, it is clear that **Option 2: Preparation of Food by Photosynthesis** is not a use of micro-organisms. Therefore, this is the correct answer.

### Final Answer:
The option that is not a use of micro-organisms is **Preparation of Food by Photosynthesis**.

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