It is safe to use telephone during a thunder 'storm.

Explanation

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks whether it is safe to use a telephone during a thunderstorm.

2. **Identifying the Risks**: During a thunderstorm, there is a risk of lightning strikes. Lightning can travel through conductive materials, including metal wires.

3. **Types of Telephones**:
- Traditional landline telephones are usually connected to outdoor wires.
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