The compounds used as refrant are:

Options

A. `NH_(3)`
B. `C Cl_(4)`
C. `CF_(4)`
D. `CF_(2)Cl_(2)`

Explanation

To solve the question regarding which compounds are used as refrigerants, we will analyze each option provided.

### Step-by-Step Solution:

1. **Understanding Refrigerants**:
- Refrigerants are substances used in cooling systems, such as refrigerators and air conditioners. They absorb heat from the environment and release it elsewhere, thereby providing a cooling effect.

2. **Analyzing the Options**:
- **Option 1: NH3 (Ammonia)**
- Ammonia is a well-known refrigerant. It has been used in industrial refrigeration systems due to its efficient heat absorption properties and relatively low cost.
- **Option 2: CCl4 (Carbon Tetrachloride)**
- Carbon tetrachloride is not commonly used as a refrigerant. It has been used in some applications but is more known for its use in fire extinguishers and as a solvent. It is not efficient or safe for refrigeration purposes.
- **Option 3: CF4 (Tetrafluoromethane)**
- Tetrafluoromethane is not typically used as a refrigerant. While it has some applications in the semiconductor industry, it is not a common refrigerant.
- **Option 4: CF2Cl2 (Dichlorodifluoromethane)**
- This compound, also known as CFC-12, is a chlorofluorocarbon (CFC) that has been widely used as a refrigerant in air conditioning and refrigeration systems. However, due to environmental concerns regarding ozone depletion, its use has been phased out in many countries.

3. **Conclusion**:
- Based on the analysis, the compounds that are used as refrigerants from the given options are:
- Option 1: NH3 (Ammonia)
- Option 4: CF2Cl2 (Dichlorodifluoromethane)

### Final Answer:
The compounds used as refrigerants are:
- NH3 (Ammonia)
- CF2Cl2 (Dichlorodifluoromethane)