Assertion : Indices of water pollution are lichens.
Reason : Lichens growth is greatly inhibited by the water pollutants .

Options

A. If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion .
B. If both Assertion and Reason are true and The Reason is not the correct explanation of the Assertion.
C. If Assertion is true but the Reason is false .
D. If both Assertion and Reason are false .

Answer

To solve the question regarding the assertion and reason about lichens as indicators of water pollution, we will follow these steps:

### Step-by-Step Solution

1. **Understand the Assertion**: The assertion states that "Indices of water pollution are lichens." This means that lichens are used as indicators to measure the level of water pollution.

2. **Evaluate the Reason**: The reason provided is "Lichens growth is greatly inhibited by the water pollutants." This suggests that the presence of water pollutants negatively affects the growth of lichens.

3. **Research on Lichens**: Lichens are symbiotic organisms made up of fungi and algae or cyanobacteria. They are known to be sensitive to air quality, particularly to pollutants like sulfur dioxide, rather than water pollutants.

4. **Analyze the Relationship**: While it is true that lichens can be affected by pollutants, they are primarily indicators of air pollution rather than water pollution. They thrive in clean environments and their absence can indicate poor air quality.

5. **Conclusion on Assertion and Reason**: Since lichens are not indicators of water pollution, the assertion is false. Additionally, while lichens can be affected by pollutants, the reason given does not correctly relate to water pollution specifically. Therefore, the reason is also false.

6. **Final Answer**: Both the assertion and the reason are false.