Name thea-amino acid which is optically inactive.

Explanation

To determine the optically inactive α-amino acid, we need to consider the structure of amino acids and the concept of chirality.

### Step-by-Step Solution:

1. **Understand the Structure of Amino Acids**:
- Amino acids have a general structure that includes an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom (H), and a variable side chain (R group) attached to a central carbon atom (α-carbon).

2. **Define Chirality**:
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