A : In presence of +ve catalyst, activation energy & threshold energy decreases.
R : Minimum energy required to permit a reaction is known as threshold energy.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion , then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion , then mark (2).
C. If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are false statements , then mark (4)

Answer

To analyze the statements given in the question, we need to evaluate both the Assertion (A) and the Reason (R) separately.

### Step 1: Understanding Assertion (A)
The assertion states that "In the presence of a positive catalyst, activation energy and threshold energy decreases."

1. **Definition of Activation Energy**: Activation energy is the minimum energy required for a reaction to occur. It is the energy barrier that must be overcome for reactants to be transformed into products.

2. **Role of a Catalyst**: A catalyst provides an alternative reaction pathway with a lower activation energy. This means that the energy required to reach the transition state is reduced, making it easier for the reaction to occur.

3. **Threshold Energy**: Threshold energy is the minimum energy required for a reaction to take place. It is essentially the energy level that reactants must reach for the reaction to proceed.

4. **Effect of Positive Catalyst**: A positive catalyst lowers both the activation energy and the threshold energy. Therefore, the assertion is correct.

### Step 2: Understanding Reason (R)
The reason states that "Minimum energy required to permit a reaction is known as threshold energy."

1. **Definition of Threshold Energy**: This statement accurately describes threshold energy. It is indeed the minimum energy that the reactants must possess for the reaction to occur.

2. **Relation to Activation Energy**: While threshold energy is the minimum energy required, activation energy is the additional energy needed to reach the transition state from the threshold level. Thus, the reason is also correct.

### Conclusion
Both the assertion and the reason are true, and the reason correctly explains the assertion.

### Final Answer
- **Assertion (A)**: True
- **Reason (R)**: True
- **Conclusion**: R is a correct explanation of A.

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