The major ozone depleting substance out of the following is

Options

A. CFCs
B. `O_(2)`
C. nitrogen
D. all of these.

Explanation

To determine the major ozone-depleting substance from the options provided, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Options**: The options given are:
- A. CFCs (Chlorofluorocarbons)
- B. O2 (Oxygen)
- C. Nitrogen
- D. All of these

2. **Understand Ozone Depletion**: Ozone depletion refers to the thinning of the ozone layer in the Earth's stratosphere, which is primarily caused by certain chemicals.

3. **Evaluate Each Option**:
- **CFCs (Chlorofluorocarbons)**: These are known to be significant contributors to ozone depletion. They release chlorine atoms when they are broken down by ultraviolet (UV) radiation, which then react with ozone (O3) and lead to its depletion.
- **O2 (Oxygen)**: Oxygen does not contribute to ozone depletion. In fact, it is a part of the ozone molecule itself.
- **Nitrogen**: While nitrogen compounds can have some impact on ozone levels, nitrogen itself does not directly deplete ozone.
- **All of these**: This option suggests that all the listed substances contribute to ozone depletion, which is incorrect based on the evaluation of the individual substances.

4. **Conclusion**: Based on the evaluation, the substance that is a major contributor to ozone depletion is CFCs.

5. **Final Answer**: The major ozone-depleting substance out of the following is **A. CFCs**.