Organisms which are indicator of `SO_(2)` pollution of air

Options

A. Mosses
B. Lichens
C. Mushrooms
D. Puffballs

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for organisms that serve as indicators of sulfur dioxide (SO₂) pollution in the air.

2. **Identifying the Options**: The options given are:
- A) Mosses
- B) Lichens
- C) Mushrooms
- D) Puffballs

3. **Defining Bioindicators**: Bioindicators are organisms that reflect the health of an environment or ecosystem. They can indicate the presence of pollutants, such as sulfur dioxide.

4. **Analyzing Each Option**:
- **Mosses**: While they can be sensitive to pollution, they are not specifically known as indicators of sulfur dioxide.
- **Lichens**: Lichens are known to be very sensitive to sulfur dioxide. They absorb SO₂ from the air, and their health can decline with increased pollution levels.
- **Mushrooms**: These are fungi that do not specifically indicate sulfur dioxide pollution.
- **Puffballs**: Similar to mushrooms, puffballs do not serve as indicators for sulfur dioxide pollution.

5. **Conclusion**: Since lichens are sensitive to sulfur dioxide and their presence or absence can indicate the level of this pollutant in the air, the correct answer is **B) Lichens**.

### Final Answer:
**B) Lichens** are the organisms that serve as indicators of sulfur dioxide pollution in the air.

---