Ozone is not present in

Options

A. thermosphere
B. Mesosphere
C. Stratosphere
D. `O_(3)` layer

Answer

To determine where ozone is not present among the given options—thermosphere, mesosphere, stratosphere, and ozone layer—let's analyze each layer of the atmosphere step by step.

### Step-by-Step Solution:

1. **Understanding the Layers of the Atmosphere**:
- The atmosphere is divided into several layers: the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
- Each layer has distinct characteristics and compositions.

2. **Identifying the Ozone Layer**:
- The ozone layer is located within the stratosphere.
- It contains a high concentration of ozone (O₃), which absorbs most of the sun's harmful ultraviolet radiation.

3. **Analyzing the Stratosphere**:
- The stratosphere is the layer above the troposphere and below the mesosphere.
- It contains ozone, particularly in the ozone layer, which is a part of the stratosphere.

4. **Examining the Mesosphere**:
- The mesosphere is located above the stratosphere and below the thermosphere.
- While it is not as rich in ozone as the stratosphere, some ozone can still be present, but in significantly lower concentrations.

5. **Looking at the Thermosphere**:
- The thermosphere is located above the mesosphere.
- This layer is characterized by very high temperatures and is where the ionosphere exists.
- Ozone is not present in significant amounts in the thermosphere.

6. **Conclusion**:
- From the analysis, we can conclude that ozone is not present in the thermosphere and to some extent in the mesosphere, but it is present in the stratosphere and the ozone layer.
- Therefore, the correct answer to the question "Ozone is not present in" is the **thermosphere**.

### Final Answer:
Ozone is not present in the **thermosphere**.