A : Ethanal undergoes aldol condensation.
R : Ethanal has four `alpha`-H atoms.

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, we need to analyze the statements A and R regarding ethanal (acetaldehyde) and its ability to undergo aldol condensation.

### Step-by-Step Solution:

1. **Understanding Aldol Condensation**:
- Aldol condensation is a reaction between aldehydes or ketones that have alpha-hydrogens. In this reaction, two molecules of the aldehyde or ketone react to form a β-hydroxy aldehyde or ketone, which can then dehydrate to form an α,β-unsaturated carbonyl compound.

2. **Identifying the Structure of Ethanal**:
- The molecular formula of ethanal is CH₃CHO. The structure can be represented as:
```
H O
\ //
C
/ \
H H
|
H
```
- In this structure, the carbon adjacent to the carbonyl group (C=O) is known as the alpha carbon.

3. **Counting Alpha-Hydrogens**:
- The alpha carbon in ethanal is the carbon that is directly bonded to the carbonyl carbon. In ethanal, the alpha carbon has three hydrogen atoms (H) attached to it.
- Therefore, ethanal has **3 alpha-hydrogens**.

4. **Evaluating Statement A**:
- Statement A claims that ethanal undergoes aldol condensation. Since ethanal has alpha-hydrogens, it can indeed undergo aldol condensation. Hence, **Statement A is true**.

5. **Evaluating Statement R**:
- Statement R claims that ethanal has four alpha-hydrogens. However, as we calculated, ethanal has only **3 alpha-hydrogens**. Therefore, **Statement R is false**.

6. **Conclusion**:
- Since Statement A is true and Statement R is false, the correct conclusion is that A is true but R is false.

### Final Answer:
- A is true, R is false.