Indicator of `SO_2` pollution is

Options

A. Algae
B. Fungi
C. Lichen
D. All of these

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the indicator of sulfur dioxide (SO₂) pollution. We need to identify which of the given options serves as an indicator for this type of pollution.

2. **Analyzing the Options**: The options provided are:
- A) Algae
- B) Fungi
- C) Lichen
- D) All of these

3. **Identifying the Correct Indicator**:
- Sulfur dioxide (SO₂) is a pollutant that can affect various organisms in the environment.
- Lichens are known to be sensitive to air quality, particularly to sulfur dioxide levels.

4. **Understanding Lichens**:
- Lichens are a symbiotic association between two different organisms: algae and fungi.
- Algae provide food through photosynthesis, while fungi provide structure and protection.

5. **Role of Lichens as Indicators**:
- When sulfur dioxide is present in the environment, it can be harmful to lichens, causing them to die.
- The absence of lichens in an area can indicate high levels of SO₂ pollution, while their presence suggests cleaner air.

6. **Conclusion**: Based on the analysis, the correct answer is C) Lichen, as it serves as a reliable indicator of sulfur dioxide pollution.

### Final Answer:
The indicator of SO₂ pollution is **C) Lichen**.

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