Select the correct option for photosynthesis in ` C_(3^(-))` plants.

Options

A. Bifunctonal nature of PEP case enzyme
B. Regeneration of each RuBP requires 6 ATP
C. First stable product of Calvin cycle undergoes phosphoylation dark reaction
D. Optimum temperture is ` 30-40^(@)C`

Answer

To solve the question regarding the correct options for photosynthesis in C3 plants, we will break down the key concepts related to the photosynthesis process, particularly focusing on the Calvin cycle and the characteristics of C3 plants.

### Step-by-Step Solution:

1. **Understanding C3 Plants**:
- C3 plants are those that primarily use the Calvin cycle for carbon fixation. They are called C3 plants because the first stable product of carbon fixation is a three-carbon compound, 3-phosphoglycerate (3-PGA).

**Hint**: Remember that C3 plants utilize the Calvin cycle for photosynthesis, resulting in a three-carbon compound.

2. **Calvin Cycle Overview**:
- The Calvin cycle involves three main phases: carbon fixation, reduction, and regeneration of ribulose bisphosphate (RuBP).
- The enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) plays a crucial role in fixing carbon dioxide in this cycle.

**Hint**: Focus on the role of rubisco in fixing carbon dioxide during the Calvin cycle.

3. **Phosphorylation in the Calvin Cycle**:
- During the Calvin cycle, the first stable product (3-PGA) undergoes phosphorylation, which is essential for the conversion of 3-PGA into glyceraldehyde-3-phosphate (G3P), a precursor for glucose and other carbohydrates.

**Hint**: Recall that phosphorylation is a key step in converting 3-PGA to G3P.

4. **Energy Requirement**:
- The Calvin cycle requires ATP and NADPH, which are produced in the light-dependent reactions of photosynthesis. Specifically, the regeneration of RuBP requires ATP.

**Hint**: ATP is crucial for the regeneration of RuBP in the Calvin cycle.

5. **Photorespiration**:
- C3 plants can also undergo photorespiration, especially under conditions of low carbon dioxide concentration. This process can lead to a loss of fixed carbon and energy, as it results in the release of CO2 without producing glucose.

**Hint**: Understand that photorespiration can affect the efficiency of photosynthesis in C3 plants.

6. **Conclusion**:
- The correct option regarding photosynthesis in C3 plants is that the first stable product of the Calvin cycle (3-PGA) undergoes phosphorylation. This is a defining characteristic of the C3 photosynthetic pathway.

**Final Answer**: The correct option is that the first stable product of the Calvin cycle undergoes phosphorylation.