Assertion: - ` 3^@` carbocations are more stable than `1^@` and `2^@` carbocations.
Reason :- The+I effect of alkyl groups decreases the magnitude of positive charge to the maximum possible extent in a `3^@` carbocation

Options

A. If both Assertion and Reason are CORRECT and Reason is the CORRECT explanation of the Assertion.
B. If both Assertion and Reason are CORRECT but Reason is not the CORRECT explanation of the Assertion.
C. If Assertion is CORRECT but Reason is INCORRECT.
D. If Assertion is INCORRECT but Reason is CORRECT.

Explanation

To solve the question regarding the stability of carbocations and the assertion and reason provided, we can break it down into the following steps:

### Step 1: Understanding Carbocations
Carbocations are positively charged carbon species. The stability of carbocations is influenced by the number of alkyl groups attached to the positively charged carbon.

### Step 2: Classifying Carbocations
Carbocations are classified based on the number of alkyl groups:
- **Primary (1°) Carbocation**: One alkyl group attached to the positively charged carbon.
- **Secondary (2°) Carbocation**: Two alkyl groups attached.
- **Tertiary (3°) Carbocation**: Three alkyl groups attached.

### Step 3: Analyzing Stability
The stability order of carbocations is:
\[ \text{3°} > \text{2°} > \text{1°} \]
This means that tertiary carbocations are more stable than secondary, which are more stable than primary carbocations.

### Step 4: Inductive Effect
The stability of carbocations can be explained by the +I (positive inductive) effect of alkyl groups. Alkyl groups are electron-donating and help to disperse the positive charge on the carbocation:
- In a **3° carbocation**, three alkyl groups donate electron density, stabilizing the positive charge effectively.
- In a **2° carbocation**, two alkyl groups provide some stabilization.
- In a **1° carbocation**, only one alkyl group is present, providing minimal stabilization.

### Step 5: Evaluating the Assertion and Reason
- **Assertion**: "3° carbocations are more stable than 1° and 2° carbocations." This is correct based on the stability order discussed.
- **Reason**: "The +I effect of alkyl groups decreases the magnitude of positive charge to the maximum possible extent in a 3° carbocation." This is also correct and explains why the 3° carbocation is the most stable.

### Conclusion
Both the assertion and reason are correct, and the reason provided is a valid explanation for the assertion.

### Final Answer
- **Assertion**: True
- **Reason**: True
- **Explanation**: The +I effect of alkyl groups stabilizes the positive charge in carbocations, making tertiary carbocations the most stable.

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