$ Grafting is always between a stock and scion.
! Movements under the effect of shock are called Seismonastic.

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

To solve the question regarding the assertion and reason statements about grafting and seismonastic movements, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Assertion**:
- The assertion states that "Grafting is always between a stock and scion."
- Grafting is a horticultural technique where a part of one plant (the scion) is attached to the root system of another plant (the stock). The stock is the part that remains in the ground and provides support and nutrients, while the scion is the part that will grow into a new plant.

2. **Understand the Reason**:
- The reason states that "Movements under the effect of shock are called seismonastic."
- Seismonastic movements refer to the non-directional movements of plants in response to mechanical stimuli, such as shock or vibration. This is a correct definition of seismonastic movements.

3. **Evaluate the Truth of the Statements**:
- Both the assertion and the reason are true statements. Grafting indeed occurs between a stock and a scion, and the definition of seismonastic movements is accurate.

4. **Determine the Relationship**:
- The next step is to determine if the reason is a correct explanation of the assertion. While both statements are true, the reason does not explain why grafting occurs between a stock and a scion. The reason discusses a different concept related to plant movements.

5. **Choose the Correct Option**:
- Based on the evaluation, we find that both the assertion and the reason are correct, but the reason does not explain the assertion. Therefore, the correct option is:
- **Option B**: Both assertion and reason are correct, but the reason is not the correct explanation of the assertion.

### Final Answer:
- The correct answer is **Option B**.

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