Starch : `alpha`-glucose :: Chitin : _______

Explanation

To solve the analogy "Starch : alpha-glucose :: Chitin : _______", we need to identify the monomer unit that makes up chitin, just as alpha-glucose is the monomer unit for starch.

### Step-by-Step Solution:

1. **Understanding Starch**:
- Starch is a polysaccharide that is primarily composed of the monomer unit known as alpha-glucose. This means that starch is formed by the polymerization of alpha-glucose molecules.

2. **Identifying Chitin**:
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