The major product `H` of the given reaction sequence is
`CH_(3) - CH_(2) CO - CH_(3) overset (Theta_(CN)) to G - overset (95% H_(2) SO_(4)) underset (Heat) to H`

Options

A. `CH_(3)-CH=underset(CH_(3))underset(|)(C)-COOH`
B. `CH_(3)-CH=underset(CH_(3))underset(|)(C)-CN`
C. `CH_(3)-CH_(2)-underset(CH_(3))underset(|)overset(OH)overset(|)(C)-COOH`
D. `CH_(3)-CH=underset(CH_(3))underset(|)(C)-CO-NH_(2)`

Explanation

To solve the question regarding the major product \( H \) of the given reaction sequence, we will break down the steps involved in the reaction of ethyl-methyl ketone with cyanide ion and subsequent treatment with sulfuric acid.

### Step-by-Step Solution:

1. **Identify the Starting Compound:**
The starting compound is ethyl-methyl ketone, which has the structure:
\[ CH_3 - CH_2 - CO - CH_3 \]
This compound can also be represented as \( C_4H_8O \).

**Hint:** Recognize the structure of the ketone and its components.

2. **Nucleophilic Addition Reaction:**
The ketone reacts with the cyanide ion (\( CN^- \)). In this reaction, the cyanide ion acts as a nucleophile and attacks the electrophilic carbon of the carbonyl group (C=O). This leads to the formation of a tetrahedral intermediate:
\[ CH_3 - CH_2 - C(OH)(CN) - CH_3 \]
After the nucleophilic attack, the oxygen carries a negative charge.

**Hint:** Remember that nucleophiles attack electrophilic centers in carbonyl compounds.

3. **Protonation of the Intermediate:**
The negatively charged oxygen in the intermediate will then pick up a proton from water or HCN, resulting in the formation of a cyanohydrin:
\[ CH_3 - CH_2 - C(OH) - CH_3 - CN \]
This compound is known as a cyanohydrin.

**Hint:** The formation of cyanohydrin involves protonation of the oxygen atom.

4. **Hydrolysis of the Cyanohydrin:**
The cyanohydrin undergoes hydrolysis when treated with 95% sulfuric acid (\( H_2SO_4 \)). The acidic conditions facilitate the conversion of the cyanohydrin into an alpha-hydroxy carboxylic acid:
\[ CH_3 - CH_2 - C(OH) - CH_3 - COOH \]
This reaction effectively converts the cyanide group into a carboxylic acid group.

**Hint:** Hydrolysis in acidic conditions transforms cyanohydrins into carboxylic acids.

5. **Final Product:**
The final product \( H \) is an alpha-hydroxy carboxylic acid with the structure:
\[ CH_3 - CH_2 - C(OH) - CH_3 - COOH \]
This compound is known as 3-hydroxybutanoic acid.

**Hint:** Identify the functional groups in the final product to confirm the structure.

### Conclusion:
The major product \( H \) of the given reaction sequence is 3-hydroxybutanoic acid.

### Answer:
The correct answer is option 3 (3-hydroxybutanoic acid).