Ozone depletion is occurring widely in

Options

A. troposphere
B. stratosphere
C. ionosphere
D. all of these.

Explanation

### Step-by-Step Solution:

1. **Understanding Ozone Depletion**: Ozone depletion refers to the thinning of the ozone layer, which is crucial for absorbing the majority of the sun's harmful ultraviolet (UV) radiation.

2. **Identifying Atmospheric Layers**: The Earth's atmosphere is divided into several layers, including the troposphere, stratosphere, ionosphere, and others. Each layer has distinct characteristics and functions.

3. **Locating the Ozone Layer**: The ozone layer is primarily located in the stratosphere, which is the second layer of the atmosphere, situated above the troposphere and below the mesosphere.

4. **Recognizing the Impact of Ozone Depletion**: The depletion of ozone is most significant in the stratosphere, particularly over the polar regions, where the phenomenon known as the "ozone hole" occurs, especially over Antarctica.

5. **Conclusion**: Based on the information, the correct answer to the question "Ozone depletion is occurring widely in" is **option B: stratosphere**.