pH values of a few solutions are given as:
Solution I : 2.2 - 2.4
Solution II : 6.8
Solution III : 7.4
Solution IV: 10
Solutions I, II, III and IV could be respectively

Options

A. Vinegar, hydrochloric acid, window cleaner and milk.
B. Curd, sodium hydroxide, milk of magnesia and coffee.
C. Lemon juice, milk, human blood and milk of magnesia
D. Glucose, nitric acid, baking soda, sodium chloride

Answer

To solve the question regarding the pH values of the given solutions, we will analyze each solution based on its pH value and identify the corresponding substances.

### Step-by-Step Solution:

1. **Identify Solution I (pH 2.2 - 2.4)**:
- The pH value of 2.2 to 2.4 indicates a highly acidic solution.
- Common substances with such low pH values include lemon juice and vinegar.
- **Conclusion**: Solution I is likely **Lemon Juice**.

2. **Identify Solution II (pH 6.8)**:
- A pH value of 6.8 is very close to neutral (pH 7) but slightly acidic.
- This pH is typical for substances like milk or some soft drinks.
- **Conclusion**: Solution II is likely **Milk**.

3. **Identify Solution III (pH 7.4)**:
- A pH value of 7.4 is slightly above neutral, indicating a weakly basic solution.
- This pH is characteristic of human blood, which is slightly alkaline.
- **Conclusion**: Solution III is likely **Human Blood**.

4. **Identify Solution IV (pH 10)**:
- A pH value of 10 indicates a basic solution.
- Substances with this pH include milk of magnesia and some cleaning agents.
- **Conclusion**: Solution IV is likely **Milk of Magnesia**.

### Final Summary:
- Solution I: **Lemon Juice**
- Solution II: **Milk**
- Solution III: **Human Blood**
- Solution IV: **Milk of Magnesia**