Select the incorrect statement.

Options

A. Ozone gas continuously formed by the action of UV rays on elementary oxygen and also degraded into molecular oxygen in the stratosphere.
B. The thickness of the ozone in a column of air from the ground to the top of the atmosphere is measured in terms of Dobson units.
C. Cl degrades ozone releasing molecular oxygen, with these atoms acting merely as catalysts.
D. Although ozone depletion is occurring widely in the stratosphere, the depletion is particularly marked over the antarctic region.

Answer

To solve the question of selecting the incorrect statement regarding ozone gas and its formation, we can break down the information provided in the video transcript step by step.

### Step-by-Step Solution:

1. **Understanding Ozone Formation**:
- Ozone (O₃) is formed in the stratosphere through the action of ultraviolet (UV) rays on molecular oxygen (O₂).
- The UV rays split molecular oxygen (O₂) into individual oxygen atoms (O). These free oxygen atoms can then react with other O₂ molecules to form ozone (O₃).

**Hint**: Remember that ozone is formed from molecular oxygen, not from elementary oxygen.

2. **Evaluating the Statements**:
- **Option 1**: Claims that ozone is formed by the action of UV rays on elementary oxygen. This is incorrect because UV rays act on molecular oxygen (O₂), not on elementary oxygen.
- **Option 2**: States that the thickness of the ozone layer is measured in Dobson units. This is a correct statement.
- **Option 3**: Mentions that chlorine degrades ozone, releasing molecular oxygen. This is correct, as chlorine from chlorofluorocarbons (CFCs) acts as a catalyst in the breakdown of ozone.
- **Option 4**: States that ozone depletion is particularly marked over the Antarctic region, which is also correct due to unique atmospheric conditions leading to significant ozone loss.

3. **Identifying the Incorrect Statement**:
- Based on the evaluations, Option 1 is the incorrect statement because it misrepresents the source of ozone formation.

### Conclusion:
The incorrect statement is **Option 1**.