What are true
(a) In `C_(4)` plants, primary `CO_(2)` acceptor is PEP
(b) PS II absorbs energy at or just below 680 mm
(c) PS I has `P_(683)`

Options

A. a, c
B. a
C. a, b
D. c

Answer

To determine which statements are true regarding photosynthesis, we will analyze each statement step by step.

### Step 1: Analyze Statement (a)
**Statement:** In C4 plants, the primary CO2 acceptor is PEP.

**Explanation:**
- In C4 plants, the first step of the carbon fixation process involves the carboxylation of phosphoenolpyruvate (PEP).
- PEP is indeed the primary CO2 acceptor in the C4 pathway, which leads to the formation of oxaloacetic acid (a 4-carbon compound).
- Therefore, this statement is **true**.

### Step 2: Analyze Statement (b)
**Statement:** PS II absorbs energy at or just below 680 nm.

**Explanation:**
- PS II, or Photosystem II, is known to absorb light energy at a wavelength of approximately 680 nanometers.
- This absorption is crucial for the process of photosynthesis as it helps in the conversion of light energy into chemical energy.
- Therefore, this statement is **true**.

### Step 3: Analyze Statement (c)
**Statement:** PS I has P683.

**Explanation:**
- PS I, or Photosystem I, actually has a reaction center that absorbs light at a wavelength of 700 nanometers, designated as P700.
- The statement incorrectly states that PS I has P683, which is not accurate.
- Therefore, this statement is **false**.

### Conclusion:
Based on the analysis:
- Statement (a) is true.
- Statement (b) is true.
- Statement (c) is false.

Thus, the correct answer is that statements (a) and (b) are true.