Fehiling's solution is

Options

A. Acidified `CuSO_(4)` solution
B. Ammonical `CuSO_(4)` solution
C. Copper sulphate + sodium hydroxide + Rochelle salt
D. Copper acetate + sodium citrate

Explanation

### Step-by-Step Text Solution:

1. **Understanding Fehling's Solution**: Fehling's solution is a chemical reagent used to test for the presence of aldehydes. It is particularly useful in distinguishing between aldehydes and ketones due to the unique reaction that aldehydes undergo with this solution.

2. **Composition of Fehling's Solution**: Fehling's solution is composed of two separate solutions, known as Fehling's solution A and Fehling's solution B.
- **Fehling's Solution A**: This is an aqueous solution of copper(II) sulfate (CuSO₄).
- **Fehling's Solution B**: This is an alkaline solution made from sodium potassium tartrate (also known as Rochelle salt) and sodium hydroxide (NaOH).

3. **Preparation of Fehling's Solution**: To prepare Fehling's solution, you need to mix equal volumes of Fehling's solution A and Fehling's solution B. This freshly prepared mixture is essential for accurate testing.

4. **Color Change Reaction**: When an aldehyde is present in the solution, it reduces the blue copper(II) ions (Cu²⁺) from the copper sulfate to form a red precipitate of copper(I) oxide (Cu₂O). This color change is a positive indication of the presence of an aldehyde.

5. **Conclusion**: Therefore, Fehling's solution consists of copper sulfate, sodium hydroxide, and sodium potassium tartrate (Rochelle salt). The correct answer to the question is option C, which lists these components.