Which one of the following UV radiations is/are moderately harmful to many organisms?

Options

A. UV-A
B. UV-B
C. UV-C
D. UV-A and B

Answer

To solve the question regarding which UV radiation is moderately harmful to many organisms, we can analyze the different types of UV radiation: UVA, UVB, and UVC.

### Step-by-Step Solution:

1. **Understand the Types of UV Radiation**:
- **UVA (320-400 nm)**: This type of UV radiation penetrates the skin deeply and is associated with skin aging and the development of skin cancers. It is considered harmful due to its ability to cause long-term damage.
- **UVB (280-320 nm)**: UVB radiation primarily affects the outer layer of the skin and is responsible for causing sunburn. It is also linked to skin cancer but is less penetrating than UVA.
- **UVC (100-280 nm)**: UVC radiation is the most harmful type of UV radiation but is mostly absorbed by the Earth's ozone layer and does not reach the surface. In artificial settings, it can cause damage to the eyes and skin.

2. **Evaluate the Harmfulness of Each Type**:
- **UVA**: Considered highly harmful due to its deep penetration and association with skin cancer and aging.
- **UVB**: Moderately harmful as it causes sunburn and can lead to skin cancer with excessive exposure.
- **UVC**: While it is harmful, its natural occurrence is limited due to ozone absorption, making its impact less relevant in everyday life.

3. **Determine the Correct Answer**:
- Since the question asks for UV radiation that is moderately harmful to many organisms, the best choice is **UVB**. UVA is highly harmful, while UVC is less relevant due to its absorption by the ozone layer.

### Conclusion:
The UV radiation that is moderately harmful to many organisms is **UVB**.