Referthe given reaction
`RuBP +O_2 overset("RuBP") underset ("Oxygenase")rarr` Phosphoglyceric acid + Phosphoglycolic and
In is the first reaction of

Options

A. `C_3` path way
B. `C_4` pathway
C. `C_2` pathway
D. Glycolysis

Answer

To solve the question regarding the given reaction involving RuBP and O2, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reaction**: The reaction provided is:
\[ \text{RuBP} + \text{O}_2 \xrightarrow{\text{RuBP oxygenase}} \text{Phosphoglyceric acid} + \text{Phosphoglycolic acid} \]
Here, RuBP (Ribulose bisphosphate) reacts with oxygen in the presence of the enzyme RuBP oxygenase (commonly known as Rubisco).

2. **Understand the Products**: The products of this reaction are phosphoglyceric acid (a 3-carbon compound) and phosphoglycolic acid (a 2-carbon compound).

3. **Recognize the Pathway**: The formation of phosphoglycolic acid indicates that this reaction is part of a specific metabolic pathway. The presence of a 2-carbon acid suggests that this is not part of the Calvin cycle but rather a different pathway.

4. **Name the Pathway**: This pathway is known as the **C2 pathway** or **photorespiration**. It occurs when the concentration of O2 is higher than that of CO2, particularly under conditions of high temperature.

5. **Identify the Context**: The C2 pathway is primarily observed in C3 plants. This is significant because it highlights the conditions under which photorespiration occurs, which can lead to a decrease in photosynthetic efficiency.

6. **Final Answer**: Therefore, the reaction described is the first reaction of the **C2 pathway**, also known as photorespiration.

### Summary:
The correct answer to the question is that the given reaction is the first reaction of the **C2 pathway** (photorespiration).