Goldsmith uses..........part of the flame for melting gold.

Options

A. outermost
B. middle
C. innermost
D. both (B) and (C)

Explanation

**Step-by-Step Solution:**

1. **Understanding the Flame Structure**: A flame consists of different zones, each with varying temperatures. The flame can be divided into three main parts:
- **Dark Zone (Inner Zone)**: This is the innermost part of the flame where incomplete combustion occurs. It is the least hot.
- **Yellow Zone (Middle Zone)**: This part of the flame is moderately hot and is visible due to the presence of soot particles.
- **Blue Zone (Outermost Zone)**: This is the outermost part of the flame where complete combustion occurs. It is the hottest part of the flame.

2. **Identifying the Requirement for Melting Gold**: Goldsmiths need to melt metals like gold and silver. To achieve this, they require a flame that can reach high temperatures.

3. **Choosing the Right Part of the Flame**: Since the blue zone of the flame is the hottest due to complete combustion, it is the most suitable for melting metals. The other zones (dark and yellow) do not provide sufficient heat for melting gold effectively.

4. **Conclusion**: Therefore, the goldsmith uses the **outermost part of the flame**, which is the blue zone, for melting gold.

**Final Answer**: Goldsmith uses the outermost part of the flame for melting gold.

---