In keys, a pair of contrasting characters is called?

Answer

To answer the question, "In keys, a pair of contrasting characters is called?", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Keys in Biology**:
- Keys are tools used in biological classification (taxonomy) to identify and differentiate organisms based on their characteristics.

2. **Identifying Contrasting Characters**:
- In the context of keys, contrasting characters refer to distinct features that can be used to differentiate between two or more organisms.

3. **Defining the Term**:
- When we have a pair of contrasting characters, this specific term used in keys is known as a "couplet".

4. **Conclusion**:
- Therefore, in keys, a pair of contrasting characters is called a couplet.

### Final Answer:
In keys, a pair of contrasting characters is called a couplet.

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