The first rate pollution monitor are

Options

A. molluscs
B. butterflies
C. honey bee
D. plants

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the first-rate pollution monitors. This implies we need to identify organisms that are effective indicators of pollution levels in the environment.

2. **Identifying Options**: The options provided are:
- Mollusk
- Butterflies
- Honey Bee
- Plants

3. **Analyzing Each Option**:
- **Mollusk**: Freshwater mollusks, such as snails and bivalves, are known to be effective bioindicators of water quality. They can accumulate pollutants and reflect the health of the aquatic ecosystem.
- **Butterflies**: While butterflies can indicate environmental changes, they are not primarily used for monitoring pollution levels in aquatic environments.
- **Honey Bee**: Honey bees are important for monitoring terrestrial environments but are not specifically known for monitoring water pollution.
- **Plants**: Some plants can indicate pollution levels, but they are not as effective as mollusks in aquatic environments.

4. **Conclusion**: Based on the analysis, the best answer is **Mollusk**, specifically freshwater mollusks, as they serve as bioindicators for both organic and inorganic pollutants in freshwater ecosystems.

5. **Final Answer**: The first-rate pollution monitor is **Mollusk**.