Which of the following statement is not correct

Options

A. ozone layer do not allow UV-B to reach the earth surface
B. ozone hole is an actual hole over antarctica
C. halons are ozone depleting substances
D. the active chlorine destroys ozone and convert it into `O_2`

Answer

To determine which statement is not correct regarding the ozone layer and its effects, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understand the Ozone Layer**: The ozone layer, composed of ozone (O3), is located in the stratosphere and serves as a protective shield for the Earth by absorbing the majority of the Sun's harmful ultraviolet (UV) radiation.

2. **Evaluate Option 1**:
- Statement: "Ozone layer does not allow UVB to reach the Earth's surface."
- Analysis: This statement is misleading. While the ozone layer significantly reduces the amount of UVB radiation that reaches the Earth's surface, it does not completely block it. Therefore, this statement is partially incorrect.

3. **Evaluate Option 2**:
- Statement: "Ozone layer protects the Earth from UV radiation."
- Analysis: This statement is correct. The ozone layer indeed protects the Earth from harmful UV radiation, including UVB and UVC rays.

4. **Evaluate Option 3**:
- Statement: "Ozone is an actual hole over Antarctica."
- Analysis: This statement is incorrect. The term "ozone hole" refers to a region where the ozone layer is significantly depleted, particularly over Antarctica during certain times of the year, but it is not a literal hole.

5. **Evaluate Option 4**:
- Statement: "The layer above Antarctica is thinning."
- Analysis: This statement is correct. The ozone layer over Antarctica has been observed to thin due to the presence of ozone-depleting substances like CFCs.

6. **Conclusion**:
- The incorrect statement among the options is Option 3: "Ozone is an actual hole over Antarctica." This is the statement that does not accurately represent the situation regarding the ozone layer.

### Final Answer:
The statement that is not correct is: **Option 3: "Ozone is an actual hole over Antarctica."**