The boiling point elevation and freezing point depression of solutions have a number of partical applications. Ethylene glycol `(CH_(2)OH-CH_(2)OH)` is used in automobile radiatiors as an antifreeze because it lowers the freezing point of the coolant. The same substance also helps to prevent the radiator coolant from boiling away by elevating the boiling point. Ethylene glycol has low vapour pressure. We can also use glycerol as an antifreeze. In order for the boiling point elevation to occur, the solute must be non-volatile, but no such restriction applies to freezing point depression. For example, methanol `(CH_(3)OH)`, a fairly volatile liquid that boils only at `65^(@)C`, is sometimes used as an antifreeze in automobile radiators.
Which of the following is a better reagent for depression in freezing point but not for elevation in boiling point?

Options

A. `CH_(3)OH`
B.
C.
D. `C_(6)H_(12)O_(6)`

Explanation

To determine which reagent is better for depression in freezing point but not for elevation in boiling point, we need to analyze the properties of the substances mentioned in the question: ethylene glycol, glycerol, and methanol.

### Step-by-Step Solution:

1. **Understand the Concepts**:
- **Freezing Point Depression**: This occurs when a solute is added to a solvent, lowering the temperature at which the solvent freezes. There are no restrictions on the volatility of the solute.
- **Boiling Point Elevation**: This occurs when a solute is added to a solvent, raising the temperature at which the solvent boils. For this to happen, the solute must be non-volatile.

2. **Identify the Substances**:
- **Ethylene Glycol (C₂H₆O₂)**: A non-volatile solute that can lower the freezing point and elevate the boiling point.
- **Glycerol (C₃H₈O₃)**: Similar to ethylene glycol, it is also a non-volatile solute that can lower the freezing point and elevate the boiling point.
- **Methanol (CH₃OH)**: A volatile liquid that can lower the freezing point but does not significantly elevate the boiling point due to its low boiling point (65°C).

3. **Evaluate the Options**:
- **Ethylene Glycol and Glycerol**: Both can lower the freezing point and elevate the boiling point, making them not suitable for the requirement of the question.
- **Methanol**: It can lower the freezing point effectively but does not elevate the boiling point significantly due to its volatility.

4. **Conclusion**:
- Methanol is the better reagent for depression in freezing point but not for elevation in boiling point. Therefore, the answer is **Methanol (CH₃OH)**.