Assertion: In `C_(3)` cycle, the first stable compound is 3C compound.
Reason: In `C_(4)` plants calvin cycle is absent.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reson are true but reason is not the correct explanation of assertion.
C. if assertion is true but reason is false.
D. If both assertion and reason are false.

Answer

To solve the question, we will analyze both the assertion and the reason provided.

### Step 1: Understanding the Assertion
The assertion states: "In C3 cycle, the first stable compound is a 3C compound."

- In the C3 photosynthetic pathway (Calvin cycle), the first stable product formed after carbon fixation is 3-phosphoglycerate (3-PGA), which is a three-carbon compound. This is true.

### Step 2: Understanding the Reason
The reason states: "In C4 plants, the Calvin cycle is absent."

- This statement is incorrect. While C4 plants do have a modified pathway for carbon fixation (the C4 pathway), they still perform the Calvin cycle. The Calvin cycle occurs in the bundle sheath cells of C4 plants after the initial fixation of carbon dioxide into a four-carbon compound (oxaloacetate).

### Step 3: Conclusion
Based on the analysis:
- The assertion is true because the first stable compound in the C3 cycle is indeed a 3-carbon compound.
- The reason is false because C4 plants do not lack the Calvin cycle; they simply have an additional step before it.

Thus, the correct answer to the question is that the assertion is true, but the reason is false.

### Final Answer
The answer is Option C: Assertion is true, but Reason is false.

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