A Water potential of distilled water is zero.
R `C_(2)` cycle is also called Kelvin cycle.

Options

A. If both As and R are correct and R is correct explanation of As
B. If both As and R are correct but R is not correct explanation of As
C. If As is correct, R is wrong
D. If both As and R are wrong.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that "the water potential of distilled water is zero."
- Water potential is defined as the potential energy of water in a system, influenced by solute concentration and pressure.
- Distilled water is pure water with no solutes, leading to a water potential of zero.

2. **Evaluating the Assertion**: Since distilled water has no solutes, its water potential is indeed zero. Therefore, the assertion is **True**.

3. **Understanding the Reason**: The reason given is that "the C2 cycle is also called the Kelvin cycle."
- The C2 cycle refers to a specific pathway of carbon fixation in plants, which is not commonly referred to as the Kelvin cycle.
- The Kelvin cycle is actually another name for the C3 cycle, which is the primary pathway for carbon fixation in most plants.

4. **Evaluating the Reason**: Since the C2 cycle is not referred to as the Kelvin cycle, the reason is **False**.

5. **Conclusion**: Since the assertion is true and the reason is false, the correct answer is that the assertion is correct while the reason is incorrect. Thus, the answer is option C: Assertion is correct, Reason is wrong.