When of the following can reduce Fehling's solution?

Options

A. Formic acid
B. Formaldehyde and acetaldehyde
C. acetic acid
D. acetaldehyde

Explanation

To determine which of the following compounds can reduce Fehling's solution, we need to understand the properties of the compounds involved. Fehling's solution is a chemical test used to differentiate between water-soluble aldehyde and ketone functional groups.

### Step-by-Step Solution:

1. **Understanding Fehling's Solution**:
- Fehling's solution consists of two solutions, Fehling's A (copper(II) sulfate) and Fehling's B (alkaline tartrate). When mixed, it forms a blue solution that can be reduced by aldehydes.

2. **Identifying Aldehydes**:
- Aldehydes are known to reduce Fehling's solution. This means any compound that has the aldehyde functional group (-CHO) can reduce the solution.

3. **Analyzing the Given Compounds**:
- If we have a list of compounds, we need to identify which of them are aldehydes. Common examples include formaldehyde (HCHO), acetaldehyde (CH3CHO), and formic acid (HCOOH).

4. **Formic Acid**:
- Formic acid (HCOOH) is a carboxylic acid but can also act as a reducing agent and can reduce Fehling's solution.

5. **Conclusion**:
- Therefore, both formaldehyde and acetaldehyde can reduce Fehling's solution, as they are aldehydes. Formic acid can also reduce it due to its reducing properties.

### Final Answer:
- The compounds that can reduce Fehling's solution are formaldehyde (HCHO), acetaldehyde (CH3CHO), and formic acid (HCOOH).