Roasting is a process in which the ore (mostly sulphide) is heated strongly in the presence of excess of air. The heating should be done at a temperature below the melting point of the ore.
Select of correct statement :

Options

A. Roasting removes easily oxidisable volatile impurities like arsenic as `As_(2) O_(3)`, antimony as `Sb_(2) O_(3)`, and sulphur as `SO_(2)`.
B. The release of `SO_(2)` (in roasting process) has been a serious air pollution problem.
C. In roasting process, if temperature is fairly low (about `500^@ C`) and the concentration of `SO_(2)` in the gaseous enviourment is more, sulphate may be produced, that is stable, and high temperature is needed to decompose it.
D. All are correct

Explanation

### Step-by-Step Solution:

1. **Understanding Roasting**:
- Roasting is a metallurgical process where sulfide ores are heated in the presence of excess air (oxygen). This process is primarily used to convert sulfide ores into oxides.

2. **Analyzing Statement A**:
- The first statement claims that roasting removes easily oxidizable volatile impurities like arsenic oxide, antimony oxide, and sulfur as sulfur dioxide. This is true because during roasting, these impurities are oxidized and released as gases.

3. **Analyzing Statement B**:
- The second statement mentions that the release of sulfur dioxide during the roasting process has become a serious pollution problem. This is also correct, as sulfur dioxide can lead to acid rain and other environmental issues.

4. **Analyzing Statement C**:
- The third statement discusses that if the temperature during roasting is low and the concentration of sulfur dioxide is high, sulfates may be produced, which are stable and require high temperatures to decompose. This statement is accurate as well.

5. **Conclusion**:
- Since all three statements (A, B, and C) are correct, the correct answer is that all of these statements are true.

### Final Answer:
- The correct answer is **D: All of these are correct**.