Assertion: Dark reaction occurs at night in the stroma of chloroplast.
Reason: All the enzymes responsible for `CO_(2)` fixation remain inactive in presence of light.

Options

A. If both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.
B. If both Assertion and Reason are true but Reason is not a correct explanation of the Assertion.
C. If Assertion and Reason are true but Reason is not a correct explanation of the Assertion.
D. If Assertion is true but the Reason is false.

Answer

To analyze the given assertion and reason, let's break it down step by step.

### Step 1: Understand the Assertion
**Assertion:** "Dark reaction occurs at night in the stroma of chloroplast."

- The dark reaction, also known as the Calvin cycle, does not strictly occur only at night. It is called a "dark reaction" because it does not require light directly to proceed. However, it can occur during the day as long as the products of the light reactions (ATP and NADPH) are available.

**Conclusion:** The assertion is **false** because dark reactions can occur during the day as well.

### Step 2: Understand the Reason
**Reason:** "All the enzymes responsible for CO2 fixation remain inactive in the presence of light."

- This statement is misleading. While some enzymes involved in CO2 fixation may have their activity regulated by light, it is not true that all enzymes become inactive in the presence of light. In fact, the light reactions produce ATP and NADPH, which are essential for driving the dark reactions.

**Conclusion:** The reason is also **false** because not all enzymes involved in CO2 fixation are inactive in light.

### Step 3: Evaluate the Relationship Between Assertion and Reason
Since both the assertion and the reason are false, we can conclude that:

- The assertion is incorrect because dark reactions can occur during the day.
- The reason is incorrect because not all enzymes responsible for CO2 fixation are inactive in light.

### Final Conclusion
Both the assertion and reason are false.

### Answer Options
Based on the analysis:
- Both assertion and reason are false.