In the given reaction
`CH_(2)-cH_(2)-overset(O)overset(||)C-CH_(2)COOC_(2)H_(5)overset([X])rarr (A) overset((i)LiAlH_(4))underset((ii)H_(2)O //H^(o+))rarr CH_(3)-CH_(2)-overset(O)overset(||)C-CH_(2)-CH_(2)OH+C_(2)H_(5)OH`
[X] will be

Options

A. `HCHO`
B. `{:(CH_(2)-OH),(|),(CH_(2)OH):},H^(o+)`
C. `{:(CH_(2)-OH),(|),(CH_(2)OH):},OH^(o+)`
D. `HCN`

Answer

To solve the given reaction and identify the reagent [X], we need to analyze the transformation step by step.

### Step 1: Analyze the Given Reaction
The initial compound is:
\[ CH_2=CH-CO-CH_2-COOC_2H_5 \]

This compound contains a double bond (alkene) and an ester functional group (COOC2H5). The reaction proceeds to form compound (A) after the addition of reagent [X].

### Step 2: Identify the Role of [X]
In the reaction, we need a reagent that can react with the alkene and the ester. The reagent [X] is likely a protecting agent or a reagent that can facilitate the formation of a more reactive intermediate.

### Step 3: Consider Possible Reagents
Given that the reaction involves a carbonyl compound and an alkene, a common reagent that can be used is ethylene glycol in the presence of an acid (H+). This can help to protect the carbonyl group and allow for further reactions.

### Step 4: Write the Reaction with [X]
The reaction with [X] can be written as:
\[ CH_2=CH-CO-CH_2-COOC_2H_5 + \text{[X]} \rightarrow \text{(A)} \]

Assuming [X] is ethylene glycol (HO-CH2-CH2-OH) in the presence of H+, we can protect the carbonyl group.

### Step 5: Reduction with Lithium Aluminum Hydride
After the reaction with [X], we treat the product with lithium aluminum hydride (LiAlH4), which is a strong reducing agent. This will reduce the ester and any remaining carbonyl groups to alcohols.

### Step 6: Hydrolysis
Finally, the product is hydrolyzed in the presence of water (H2O) and H+ to yield the final products:
\[ CH_3-CH_2-C(=O)-CH_2-CH_2OH + C_2H_5OH \]

### Conclusion
Thus, the reagent [X] that facilitates the transformation is:
\[ \text{[X] = Ethylene glycol (HO-CH2-CH2-OH) in the presence of H+} \]

### Summary of Steps:
1. Analyze the initial compound and its functional groups.
2. Identify the role of [X] in the reaction.
3. Consider possible reagents that can react with both the alkene and the ester.
4. Write the reaction with [X].
5. Describe the reduction and hydrolysis steps.
6. Conclude with the identification of [X].