Smog is consequence of

Options

A. rapid build of `CO_(2)` in atmosphere
B. depletion of ozone layer
C. presence of high pressure in atmosphere
D. rapid build up of photochemical oxidants, pollutants and thermal inversions

Answer

### Step-by-Step Solution:

1. **Understanding Smog**: Smog is a type of air pollution that is a mixture of smoke and fog. It typically occurs in urban areas and can have serious health effects.

2. **Identifying Causes of Smog**: To determine the cause of smog, we need to analyze the options provided:
- **Option A**: Rapid build-up of carbon dioxide in the atmosphere.
- **Option B**: Depletion of the ozone layer.
- **Option C**: Presence of high pressure in the atmosphere.
- **Option D**: Rapid build-up of photochemical oxidant pollutants and thermal inversion.

3. **Evaluating Each Option**:
- **Option A**: While carbon dioxide is a greenhouse gas, its rapid build-up is not directly linked to the formation of smog.
- **Option B**: Depletion of the ozone layer primarily affects UV radiation levels and is not a direct cause of smog.
- **Option C**: High atmospheric pressure can influence weather patterns but is not a primary cause of smog.
- **Option D**: Photochemical oxidants, such as volatile organic compounds (VOCs), react with nitrogen oxides in the presence of sunlight to form smog. Thermal inversion traps these pollutants close to the ground, exacerbating the smog conditions.

4. **Conclusion**: Based on the analysis, the correct answer is **Option D**: rapid build-up of photochemical oxidant pollutants and thermal inversion.