Milk can be preserved by adding a few drops of

Options

A. Formic acid solution
B. Formaldehyde solution
C. Acetic acid solution
D. Acetaldehyde solution

Answer

To solve the question of how milk can be preserved by adding a few drops of a specific solution, we need to analyze the options given and understand the role of each substance in preserving milk.

### Step-by-Step Solution:

1. **Understanding the Options**:
- The options provided are:
a. Formic acid solution
b. Formaldehyde solution
c. Acetic acid solution
d. Acetaldehyde solution

2. **Analyzing Each Option**:
- **Formic Acid**: This is a weak acid and may not be effective in preserving milk against microbial growth.
- **Formaldehyde**: This is a strong preservative and has antimicrobial properties. It can inhibit microbial growth effectively, making it a suitable choice for preservation.
- **Acetic Acid**: While it can act as a preservative (like in vinegar), it is not as effective as formaldehyde in preventing microbial growth in milk.
- **Acetaldehyde**: This compound is not commonly used for preserving milk and does not have strong antimicrobial properties.

3. **Choosing the Best Option**:
- Based on the analysis, **formaldehyde solution** is the most effective option for preserving milk due to its ability to act as an emulsifier and its strong antimicrobial properties.

4. **Conclusion**:
- Therefore, the correct answer is **b. Formaldehyde solution**.