Name the first product of `CO_(2)` fixation in `C_(4)` pathway.

Explanation

### Step-by-Step Solution:

1. **Understand the C4 Pathway**: The C4 pathway is a photosynthetic process that occurs in certain plants, allowing them to efficiently fix carbon dioxide (CO2) in conditions where it might be less available.

2. **Identify the First Product of CO2 Fixation**: In the C4 pathway, the first stable product formed after the fixation of CO2 is a four-carbon compound.

3. **Name the Four-Carbon Compound**: This four-carbon compound is known as **oxaloacetic acid**, often abbreviated as **OAA**.

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