Which melts in boiling water :

Options

A. Bell metal
B. Monel metal
C. Wood' metal
D. Gun metal

Explanation

To determine which metal melts in boiling water, we need to compare the melting points of the given options with the boiling point of water, which is 100 degrees Celsius.

### Step-by-Step Solution:

1. **Understand the Question**: We need to identify which of the listed metals has a melting point lower than or equal to 100 degrees Celsius, as only then can it melt in boiling water.

2. **Analyze Each Option**:
- **Option 1: Bell Metal**
- Bell metal is an alloy primarily composed of copper (around 78%) and tin (around 22%).
- **Melting Point**: Approximately 840 to 971 degrees Celsius.
- **Conclusion**: Bell metal does not melt in boiling water.

- **Option 2: Monal Metal**
- Monal metal is an alloy of nickel and copper, with small amounts of iron, manganese, carbon, and silicon.
- **Melting Point**: Approximately 1300 to 1350 degrees Celsius.
- **Conclusion**: Monal metal does not melt in boiling water.

- **Option 3: Woods Metal**
- Woods metal is an alloy of bismuth, lead, tin, and cadmium.
- **Melting Point**: Approximately 70 degrees Celsius.
- **Conclusion**: Woods metal will melt in boiling water.

- **Option 4: Gun Metal**
- Gun metal is an alloy of tin and zinc.
- **Melting Point**: Approximately 1000 degrees Celsius.
- **Conclusion**: Gun metal does not melt in boiling water.

3. **Final Decision**: Based on the melting points analyzed, the only metal that melts in boiling water (100 degrees Celsius) is **Woods Metal**.

### Answer:
**Option 3: Woods Metal**