Assertion :- Long distance transport of substances within plant cannot be by diffusion alone.
Reason:- Diffusion is a slow process

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 solve the question regarding the assertion and reason about the transport of substances in plants, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Long distance transport of substances within plants cannot be by diffusion alone."
- This means that for substances to travel long distances within a plant, other mechanisms must be involved in addition to diffusion.

2. **Understanding the Reason**:
- The reason provided is that "Diffusion is a slow process."
- This implies that because diffusion is slow, it is not suitable for transporting substances over long distances quickly.

3. **Evaluating the Assertion**:
- The assertion is true because diffusion, while effective for short distances, is not efficient for long distances due to its slow nature.

4. **Evaluating the Reason**:
- The reason is also true. Diffusion does take time, and the time taken for a molecule to diffuse across a typical plant cell can be significant (e.g., about 2.5 seconds).

5. **Determining the Relationship**:
- Since both the assertion and the reason are true, we need to assess if the reason correctly explains the assertion.
- The reason does explain why diffusion alone is not sufficient for long-distance transport, as its slow nature limits its effectiveness.

6. **Conclusion**:
- Therefore, both the assertion and reason are true, and the reason is the correct explanation of the assertion. The correct answer is option 1.

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

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