Assertion :- In `C_(4)` plants `CO_(2)` always transports to bundle sheath cells from mesophyll cells in the form of malic acid
Reason :- OAA is always reduced into malic acid in `C_(4)` plants

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason 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 analyze the assertion and reason provided in the question, we will break down the concepts related to C4 plants, their carbon fixation process, and the relationship between the assertion and reason.

### Step-by-Step Solution:

1. **Understanding C4 Plants**:
- C4 plants are specialized plants that have adapted to hot and dry environments. They utilize a unique photosynthetic pathway known as the C4 pathway, which is efficient in carbon fixation.

**Hint**: Remember that C4 plants are adapted to specific environmental conditions.

2. **Carbon Fixation in C4 Plants**:
- In C4 plants, the initial carbon fixation occurs in mesophyll cells. Here, carbon dioxide (CO2) is fixed into a four-carbon compound called oxaloacetate (OAA) using the enzyme phosphoenolpyruvate carboxylase (PEP carboxylase).

**Hint**: Identify the enzyme responsible for the first step of carbon fixation in C4 plants.

3. **Conversion of OAA**:
- The oxaloacetate (OAA) formed is then converted into malate (malic acid). This conversion is crucial as malate is the form in which CO2 is transported from mesophyll cells to bundle sheath cells.

**Hint**: Focus on the transformation of OAA into malate and its significance in transport.

4. **Transport to Bundle Sheath Cells**:
- The malate is transported to the bundle sheath cells, where it is decarboxylated to release CO2. This CO2 is then used in the Calvin cycle (C3 cycle) for further fixation and ultimately for glucose production.

**Hint**: Understand the role of malate in transporting carbon to the bundle sheath cells.

5. **Evaluating the Assertion**:
- The assertion states that in C4 plants, CO2 is always transported to bundle sheath cells from mesophyll cells in the form of malic acid. This is true because malate is indeed the form in which CO2 is transported.

**Hint**: Confirm whether the assertion accurately describes the transport mechanism in C4 plants.

6. **Evaluating the Reason**:
- The reason states that OAA is always reduced into malic acid in C4 plants. This is also true, as OAA is converted to malate in the mesophyll cells.

**Hint**: Determine if the reason correctly explains the process mentioned in the assertion.

7. **Conclusion**:
- Both the assertion and the reason are true, and the reason provides a correct explanation for the assertion. Therefore, the correct answer is that both the assertion and reason are true, and the reason is the correct explanation of the assertion.

**Hint**: Summarize the relationship between the assertion and reason to arrive at the final conclusion.

### Final Answer:
Both the assertion and reason are true, and the reason is the correct explanation of the assertion.