Name a natural elastomer.

Explanation

**Step-by-Step Solution:**

1. **Understanding Elastomers**:
- An elastomer is a type of polymer that has the ability to stretch and return to its original shape when the force is removed. This property is known as stretchability.

2. **Identifying Natural Elastomers**:
- Natural elastomers are those that occur in nature and are derived from natural sources.

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