Coke is not used in the preparation of

Options

A. `CO+H_2`
B. `CO+N_2`
C. iron
D. diamond

Explanation

To answer the question "Coke is not used in the preparation of," we can analyze the information provided in the video transcript step by step.

### Step-by-Step Solution:

1. **Understanding Coke**:
- Coke is a form of carbon that is produced by heating coal in the absence of air. It is primarily used as a fuel and a reducing agent in various chemical processes.

**Hint**: Remember that coke is a solid form of carbon produced from coal.

2. **Uses of Coke**:
- The transcript mentions that coke is used in the formation of water gas (CO + H2) and producer gas (CO + N2). This is done by passing steam or reacting carbon with oxygen and nitrogen.

**Hint**: Identify the processes where coke acts as a reactant or reducing agent.

3. **Coke in Metallurgy**:
- Coke is also used in the blast furnace for the reduction of iron ore, where it acts as a reducing agent to convert iron oxides into iron.

**Hint**: Consider the role of coke in metal extraction processes.

4. **Coke and Diamond**:
- The transcript specifically states that coke is not used in the preparation of diamonds. Diamonds are a crystalline form of carbon, but their formation occurs under high pressure and temperature conditions deep within the Earth, not through the use of coke.

**Hint**: Think about the natural formation of diamonds compared to industrial processes involving coke.

5. **Conclusion**:
- Based on the information, we conclude that coke is not used in the preparation of diamonds.

### Final Answer:
Coke is not used in the preparation of diamonds.