`SO_(2)` pollution is indicated by

Options

A. Desmodium (grasses)
B. Sphagnum (mosses)
C. Usnea.(lichens)
D. Cucurbita (climbers)

Answer

To determine what indicates SO₂ (sulfur dioxide) pollution, we can follow these steps:

### Step 1: Understand the Context of SO₂ Pollution
Sulfur dioxide (SO₂) is a significant air pollutant that can have harmful effects on the environment and human health. It is primarily produced from industrial processes, vehicle emissions, and the burning of fossil fuels.

### Step 2: Identify Organisms Sensitive to SO₂
Certain organisms are sensitive to air pollution, particularly sulfur dioxide. These organisms can serve as bioindicators of pollution levels in the environment.

### Step 3: Analyze the Given Options
The options provided are:
- A) Basmodium (grasses)
- B) Sphagnum (mosses)
- C) Asnea (lichens)
- D) Cucurbita (cucumbers)

### Step 4: Evaluate Each Option
- **Basmodium (grasses)**: Grasses are generally not sensitive indicators of SO₂ pollution.
- **Sphagnum (mosses)**: While mosses can indicate certain environmental conditions, they are not specifically sensitive to SO₂.
- **Asnea (lichens)**: Lichens are well-known bioindicators of air quality. They are very sensitive to sulfur dioxide and other pollutants. Their presence or absence can indicate the level of air pollution.
- **Cucurbita (cucumbers)**: Cucumbers are not indicators of air pollution.

### Step 5: Conclusion
Based on the sensitivity of the organisms to sulfur dioxide, the correct answer is **C) Asnea (lichens)**. The absence of lichens in polluted areas indicates high levels of SO₂, while their presence in cleaner areas suggests lower pollution levels.

### Final Answer
SO₂ pollution is indicated by **C) Asnea (lichens)**.

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