In the reaction
X + Y `underset(5^(@)C)overset(NaOH)(rarr) CH_(3)-overset(OH)overset(|)(CH)-underset(CH_(3))underset(|)(CH)-CHO`
(X) and (Y) Will respectively be :

Options

A. `CH_(3)–CH_(2)`–CHO and `CH_(3)–CH_(2)`–CHO
B. `CH_(3)`–CHO and `CH_(3)–CH_(2)`–CHO
C. `CH_(3)`–CHO and `CH_(3)`–CHO
D. `CH_(3)`-CHO and `CH_(3)-underset(CH_(3))underset(|)overset(CH_(3))overset(|)(C ) - CHO`

Answer

To determine the reactants X and Y in the given reaction, we need to analyze the product formed and the conditions under which the reaction occurs. The product is a result of aldol condensation, which typically involves the reaction of two aldehydes or ketones in the presence of a base.

### Step-by-Step Solution:

1. **Identify the Product**: The product given is CH3-CH(OH)-CH(CH3)-CHO. This structure indicates that it is a β-hydroxy aldehyde, which is a common intermediate in aldol condensation reactions.

2. **Understand Aldol Condensation**: Aldol condensation occurs when two carbonyl compounds (aldehydes or ketones) react in the presence of a base (like NaOH) to form a β-hydroxy carbonyl compound, which can further dehydrate to form an α,β-unsaturated carbonyl compound.

3. **Analyze the Structure of the Product**: The product has:
- A hydroxyl group (-OH) attached to the second carbon (β-position).
- An aldehyde group (-CHO) at the end of the carbon chain.
- Two methyl groups (CH3) indicating that one of the reactants must be a compound that can provide these groups.

4. **Determine Possible Reactants**:
- The presence of the aldehyde group suggests that one of the reactants is likely an aldehyde.
- The other reactant must also be a carbonyl compound capable of forming the β-hydroxy aldehyde.

5. **Choose Reactants**:
- Let's consider the reactants CH3CHO (acetaldehyde) and CH3CH2CHO (butanal).
- When CH3CHO reacts with CH3CH2CHO in the presence of NaOH, the aldol condensation can occur.

6. **Reaction Mechanism**:
- The base (NaOH) will deprotonate the alpha hydrogen of one of the aldehydes, forming an enolate ion.
- This enolate will then attack the carbonyl carbon of the other aldehyde, leading to the formation of the β-hydroxy aldehyde.

7. **Final Verification**:
- The product formed from the reaction of CH3CHO and CH3CH2CHO matches the given product structure, confirming that these are indeed the correct reactants.

### Conclusion:
Thus, the reactants X and Y are:
- **X = CH3CHO (Acetaldehyde)**
- **Y = CH3CH2CHO (Butanal)**