The reagent which does not react with both, acetone and benzaldehyde is ______ .

Options

A. sodium hydrogensulphite.
B. phenyl hydrazine
C. Fehling's solution
D. Grignard reagent

Explanation

To determine the reagent that does not react with both acetone and benzaldehyde, we need to analyze the reactivity of the given reagents with these compounds.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- Acetone (CH₃COCH₃) is a ketone.
- Benzaldehyde (C₆H₅CHO) is an aromatic aldehyde.

2. **Review the Given Reagents**:
- The question implies that we have multiple reagents to consider, including sodium hydrogen sulfide, phenylhydrazine, Fehling's solution, and Grignard reagent.

3. **Analyze Each Reagent**:
- **Sodium Hydrogen Sulfide (NaHS)**: This reagent can undergo nucleophilic addition reactions with both acetone and benzaldehyde. Therefore, it reacts with both.
- **Phenylhydrazine**: This reagent is known to react with both aldehydes and ketones through nucleophilic addition-elimination reactions. Hence, it also reacts with both acetone and benzaldehyde.
- **Fehling's Solution**: This reagent is specifically used to test for aldehydes. It does not react with ketones. Therefore, it does not react with acetone (ketone) or benzaldehyde (aldehyde).
- **Grignard Reagent (RMgX)**: Grignard reagents are strong nucleophiles and will react with both acetone and benzaldehyde, leading to nucleophilic addition reactions.

4. **Conclusion**:
- Among the reagents analyzed, **Fehling's solution** is the only one that does not react with both acetone and benzaldehyde. Thus, the answer is **Fehling's solution**.

### Final Answer:
The reagent which does not react with both acetone and benzaldehyde is **Fehling's solution**.