`CaCl_(2)` is preferred over NaCl for clearing ice on roads particularly in very cold countries. This is because:

Options

A. `CaCl_(2)` is less soluble in `H_(2)O ` than NaCl
B. `CaCl_(2)` is hygroscopic but NaCl is not
C. Eutectic mixture of `CaCl_(2)"/"H_(2)O` freezes at `-55^(@)C` while that of `NaCl"/"H_(2)O` freezes at `-18^(@)C`
D. `NaCl` makes the road slipperty but `CaCl_(2)` does not

Explanation

To understand why `CaCl2` is preferred over `NaCl` for clearing ice on roads, particularly in very cold countries, we can analyze the properties and behaviors of these compounds when they are used for de-icing.

### Step-by-Step Solution:

1. **Understanding the Problem**:
- The question asks why `CaCl2` is preferred over `NaCl` for clearing ice on roads in cold climates.

2. **Solubility in Water**:
- It is important to note that `CaCl2` is more soluble in water than `NaCl`. When dissolved, `CaCl2` dissociates into calcium ions (Ca²⁺) and chloride ions (Cl⁻), which can help lower the freezing point of water.

3. **Hygroscopic Nature**:
- `CaCl2` is hygroscopic, meaning it can absorb moisture from the air. This property allows it to attract water, which can help in melting ice more effectively compared to `NaCl`, which is also hygroscopic but to a lesser extent.

4. **Freezing Point Depression**:
- The key reason for using `CaCl2` is its ability to lower the freezing point of water significantly. When mixed with water, a solution of `CaCl2` can remain liquid at temperatures as low as -55 degrees Celsius, while a solution of `NaCl` only remains liquid down to about -18 degrees Celsius. This is due to the formation of a eutectic mixture, which prevents the formation of ice at lower temperatures.

5. **Effect on Road Conditions**:
- While both salts can make roads slippery, `CaCl2` is more effective in preventing ice formation and maintaining a liquid state at lower temperatures, making it more suitable for de-icing in very cold conditions.

6. **Conclusion**:
- Therefore, the primary reason `CaCl2` is preferred over `NaCl` for clearing ice on roads is its ability to lower the freezing point of water significantly, making it more effective in extremely cold conditions.

### Final Answer:
`CaCl2` is preferred over `NaCl` for clearing ice on roads in very cold countries because a mixture of `CaCl2` and water freezes at -55 degrees Celsius, while a mixture of `NaCl` and water freezes at -18 degrees Celsius, allowing `CaCl2` to remain effective at much lower temperatures.