In photosynthesis `CO_(2)` combines with:

Options

A. ATP
B. RuBP
C. PGA
D. PGAL

Answer

To answer the question "In photosynthesis, CO₂ combines with:", we will analyze the options provided and determine which one is correct.

### Step-by-Step Solution:

1. **Understanding Photosynthesis**:
- Photosynthesis is the process by which green plants convert light energy into chemical energy, using carbon dioxide (CO₂), water, and minerals to produce oxygen and energy-rich organic compounds.

2. **Analyzing the Options**:
- **Option 1: ATP (Adenosine Triphosphate)**:
- ATP is a product of the light-dependent reactions of photosynthesis. It is not a reactant that combines with CO₂. Therefore, this option is incorrect.

- **Option 2: RUBP (Ribulose Bisphosphate)**:
- During the dark phase (Calvin Cycle) of photosynthesis, CO₂ combines with RUBP in a reaction catalyzed by the enzyme rubisco (ribulose 1,5-bisphosphate carboxylase). This reaction is known as carboxylation, and it produces 3-PGA (3-phosphoglyceric acid), which is the first stable product of this phase. This option is correct.

- **Option 3: PGA (3-Phosphoglyceric Acid)**:
- PGA is the product formed after CO₂ reacts with RUBP. It is not the molecule that CO₂ combines with, so this option is incorrect.

- **Option 4: PGAL (3-Phosphoglyceraldehyde)**:
- PGAL, also known as glyceraldehyde 3-phosphate, is a product that can be derived from PGA. It is not the initial reactant that CO₂ combines with, making this option incorrect as well.

3. **Conclusion**:
- Based on the analysis, the correct answer to the question "In photosynthesis, CO₂ combines with" is **RUBP (Ribulose Bisphosphate)**.

### Final Answer:
CO₂ combines with RUBP (Ribulose Bisphosphate) during photosynthesis.

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