Solder is an alloy of

Options

A. `70%` lead, `30%` tin
B. `30%` lead, `70%` tin
C. `80%` lead, `20%` tin
D. `90%` Cu, `10%` tin

Explanation

To determine the composition of solder, we need to understand what solder is and its typical components.

### Step-by-Step Solution:

1. **Definition of Solder**: Solder is an alloy that is primarily used for joining metal pieces together, especially in electronics and plumbing.

2. **Components of Solder**: The most common type of solder is made from a combination of tin (Sn) and lead (Pb).

3. **Typical Composition**: The typical composition of solder is approximately 60% tin and 40% lead, but variations exist. In some formulations, solder can contain around 30% lead and 70% tin.

4. **Analyzing the Options**:
- **Option 1**: 70% lead and 30% tin - This is not a common composition for solder.
- **Option 2**: 30% lead and 70% tin - This is a valid composition for solder and is commonly used.
- **Option 3**: 90% copper and 10% tin - This is not a typical solder composition.

5. **Conclusion**: Based on the analysis, the correct answer is **Option 2: 30% lead and 70% tin**.

### Final Answer:
Solder is an alloy of 30% lead and 70% tin.

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