Assertion : In perennial plant species, it is difficult to define vegetative, reproductive and senescent phases.
Reason : Perennial plants have very short life span.

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.

Explanation

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that in perennial plant species, it is difficult to define vegetative, reproductive, and senescent phases.
- This implies that the life cycle stages of these plants are not clearly distinguishable.

2. **Understanding the Reason**:
- The reason provided is that perennial plants have a very short lifespan.
- This suggests that their life cycle is quick, which would typically allow for clear identification of different phases.

3. **Defining Perennial Plants**:
- Perennial plants are defined as those that complete their life cycle in more than two years.
- They can live for several years, often going through multiple cycles of growth and reproduction.

4. **Analyzing the Life Cycle Stages**:
- **Vegetative Phase**: This is when the plant grows and develops leaves and stems.
- **Reproductive Phase**: This is when the plant produces flowers, seeds, and fruits.
- **Senescent Phase**: This is when the plant's metabolic processes slow down as it ages.

5. **Evaluating the Assertion**:
- Given that perennial plants live for several years, it can indeed be challenging to distinctly categorize their life stages since they may overlap significantly over time.

6. **Evaluating the Reason**:
- The reason states that perennial plants have a short lifespan, which is incorrect. Perennial plants typically have a long lifespan.
- Therefore, the reason does not correctly explain the assertion.

7. **Conclusion**:
- The assertion is true (it is difficult to define the phases in perennial plants), but the reason is false (perennial plants do not have a short lifespan).
- Thus, the correct answer is that the assertion is true, but the reason is false.

### Final Answer:
- Assertion: True
- Reason: False
- Correct Option: C

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