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 solve the question regarding the correctness of statements about photosynthesis, we will evaluate each statement one by one.

### Step 1: Evaluate Statement I
**Statement I:** In C3 plants, the primary CO₂ acceptor is RuBP.

- **Analysis:** In C3 plants, the primary carbon dioxide acceptor is indeed Ribulose bisphosphate (RuBP). This is the first step in the Calvin cycle where CO₂ is fixed.
- **Conclusion:** This statement is **correct**.

### Step 2: Evaluate Statement II
**Statement II:** In the photosynthetic process, PS-II absorbs energy at or just below 680 nm.

- **Analysis:** Photosystem II (PS-II) primarily absorbs light in the wavelength range of around 680 nm. It is known for its peak absorption at this wavelength.
- **Conclusion:** This statement is **correct**.

### Step 3: Evaluate Statement III
**Statement III:** The chlorophyll-a that is present in photosystem-I has absorption maxima at 680 nm.

- **Analysis:** Chlorophyll-a in Photosystem I (PS-I) actually has its absorption maximum at around 700 nm, not 680 nm. This is a common misconception.
- **Conclusion:** This statement is **incorrect**.

### Final Conclusion
- **Correct Statements:** I and II are correct.
- **Incorrect Statement:** III is incorrect.

Thus, the correct answer to the question is that statements I and II are correct.

### Answer:
The correct option is **4** (I and II only).

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