What is the basis for designating `C_(3)` and `C_(4)` pathways of photosynthesis ?

Explanation

To understand the basis for designating the C3 and C4 pathways of photosynthesis, we need to look at the key differences in the processes and the compounds involved in each pathway.

### Step-by-Step Solution:

1. **Definition of C3 Pathway**:
- The C3 pathway, also known as the Calvin cycle, is the most common photosynthetic pathway. It is called C3 because the first stable product formed during carbon fixation is a 3-carbon compound called 3-phosphoglyceric acid (3-PGA).

2. **Process of C3 Pathway**:
...