A : Benzaldehyde is more reactive towards nucleophilic addition than acetaldehyde.
R : Benzaldehyde has less steric hindrance than acetaldehyde.

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 solve the question regarding the reactivity of benzaldehyde and acetaldehyde towards nucleophilic addition, we will analyze both the assertion (A) and the reason (R) provided.

### Step 1: Analyze the Assertion (A)
**Assertion:** Benzaldehyde is more reactive towards nucleophilic addition than acetaldehyde.

- **Explanation:** Nucleophilic addition reactions occur at the carbonyl carbon, which is positively polarized due to the electronegativity of the oxygen atom. In benzaldehyde, the carbonyl carbon is less positively charged compared to that in acetaldehyde due to resonance stabilization from the phenyl group. The resonance in benzaldehyde allows the π electrons to delocalize, reducing the positive character of the carbonyl carbon. Therefore, benzaldehyde is actually less reactive towards nucleophilic addition than acetaldehyde.

**Conclusion:** The assertion is **false**.

### Step 2: Analyze the Reason (R)
**Reason:** Benzaldehyde has less steric hindrance than acetaldehyde.

- **Explanation:** Steric hindrance refers to the crowding around a reactive site, which can affect the reactivity of a molecule. Acetaldehyde has a methyl group (which is relatively small) attached to the carbonyl carbon, while benzaldehyde has a phenyl group (which is bulkier). The presence of the larger phenyl group in benzaldehyde increases steric hindrance compared to the smaller methyl group in acetaldehyde. Therefore, benzaldehyde actually has **more** steric hindrance than acetaldehyde.

**Conclusion:** The reason is also **false**.

### Step 3: Final Conclusion
Since both the assertion and the reason are false, the correct answer is that both A and R are false.

### Summary of the Solution:
- Assertion (A) is false: Benzaldehyde is **less** reactive towards nucleophilic addition than acetaldehyde.
- Reason (R) is false: Benzaldehyde has **more** steric hindrance than acetaldehyde.