`{:(" "OH),(" |"),(Ph-C-CH_(3)),(" |"),(" "CH_(2)-CH_(3)):}`
Which of the following combinations can not be used to prepare alcohol given above ?

Options

A. `PhMgBr + "2 -butanone" underset(NH_(4)Cl)rarr`
B. `EtMgBr + Ph - overset(O)overset(||)(C)-CH_(3) underset(NH_(4)Cl)rarr`
C. `CH_(3)MgBr + Ph - overset(O)overset(||)(C)-Et underset(NH_(4)Cl)rarr`
D. `EtMgBr + Ph - overset(O)overset(||)(C)-CH_(2)-CH_(3)underset(NH_(4)Cl)rarr`

Explanation

To determine which combination cannot be used to prepare the given alcohol structure, we will analyze the reactions of Grignard reagents with various carbonyl compounds step by step.

### Given Structure:
The alcohol structure can be represented as:
```
OH
|
Ph-C-CH3
|
CH2-CH3
```
Where:
- Ph = Phenyl group (C6H5)
- CH3 = Methyl group
- CH2-CH3 = Ethyl group

### Step 1: Identify the Grignard Reagents and Carbonyl Compounds
We will analyze the four combinations (A, B, C, D) to see which one does not yield the desired alcohol.

1. **Combination A**: Ph-MgBr with 2-butanone (CH3C(=O)CH2CH3)
2. **Combination B**: Et-MgBr with benzophenone (PhC(=O)Ph)
3. **Combination C**: Me-MgBr with ethyl phenyl ketone (PhC(=O)CH2CH3)
4. **Combination D**: Et-MgBr with acetophenone (PhC(=O)CH3)

### Step 2: Analyze Each Reaction
#### Combination A:
- **Grignard Reagent**: Ph-MgBr
- **Carbonyl Compound**: 2-butanone (CH3C(=O)CH2CH3)
- Reaction:
- Ph- (C6H5) will act as a nucleophile and attack the carbonyl carbon of 2-butanone.
- The product will be:
```
Ph-C(OH)(CH3)(CH2CH3)
```
- This yields the desired alcohol.

#### Combination B:
- **Grignard Reagent**: Et-MgBr
- **Carbonyl Compound**: Benzophenone (PhC(=O)Ph)
- Reaction:
- Et- (C2H5) will attack the carbonyl carbon of benzophenone.
- The product will be:
```
Ph-C(OH)(C2H5)(Ph)
```
- This does not yield the desired alcohol.

#### Combination C:
- **Grignard Reagent**: Me-MgBr
- **Carbonyl Compound**: Ethyl phenyl ketone (PhC(=O)CH2CH3)
- Reaction:
- Me- (CH3) will attack the carbonyl carbon of ethyl phenyl ketone.
- The product will be:
```
Ph-C(OH)(CH3)(CH2CH3)
```
- This yields the desired alcohol.

#### Combination D:
- **Grignard Reagent**: Et-MgBr
- **Carbonyl Compound**: Acetophenone (PhC(=O)CH3)
- Reaction:
- Et- (C2H5) will attack the carbonyl carbon of acetophenone.
- The product will be:
```
Ph-C(OH)(C2H5)(CH3)
```
- This does not yield the desired alcohol.

### Conclusion:
The combination that cannot be used to prepare the given alcohol is **Combination B** (Et-MgBr with benzophenone) and **Combination D** (Et-MgBr with acetophenone). However, since the question asks for a single combination, we can conclude that **Combination B** is the most distinct as it does not yield the desired structure at all.

### Final Answer:
**Combination B: Et-MgBr with benzophenone cannot be used to prepare the given alcohol.**