Which of the following statements with regard to photosynthesis is/are correct?
I. In C3 plants, the primary `CO_2` acceptor is RuBP.
II. In the photosynthetic process, PS-II absorbs energy at or just below 680 nm.
III. The chlorophyll-a that is present in the photosystem-I has absorption maxima at 680nm.

Options

A. II and III only
B. I only
C. III only
D. I and II only

Answer

To determine which statements regarding photosynthesis are correct, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement I: In C3 plants, the primary CO2 acceptor is RuBP.**
- In C3 plants, during the Calvin cycle, the primary CO2 acceptor is indeed Ribulose bisphosphate (RuBP). When CO2 is fixed, it combines with RuBP to form 3-phosphoglycerate (3-PGA). Therefore, this statement is **correct**.

2. **Statement II: In the photosynthetic process, PS-II absorbs energy at or just below 680 nm.**
- Photosystem II (PS-II) is known to absorb light most efficiently at a wavelength of around 680 nm. Therefore, this statement is also **correct**.

3. **Statement III: The chlorophyll-a that is present in photosystem-I has absorption maxima at 680 nm.**
- Photosystem I (PS-I) actually has its absorption maximum at around 700 nm, not 680 nm. Therefore, this statement is **incorrect**.

### Conclusion:
- The correct statements are I and II. Thus, the answer is that the correct options are **I and II only**.

### Final Answer:
The correct statements with regard to photosynthesis are **I and II**.

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