Most harmful type of environmental pollutants are

Options

A. Human organic wastes
B. Natural nutrients in excess
C. Waste animal feed
D. Nonbiodegradable chemicals.

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the most harmful type of environmental pollutants among the given options.

2. **Analyzing the Options**:
- **Option A: Human Organic Waste**: This can lead to water pollution due to pathogens like E.coli, but it can decompose over time.
- **Option B: Natural Nutrients in Excess**: Excess nutrients can cause algal blooms, leading to water pollution, but they are biodegradable.
- **Option C: Waste Animal Feed**: This also contributes to water pollution but is biodegradable.
- **Option D: Non-Biodegradable Chemicals**: These include substances like plastics that do not decompose and can persist in the environment for hundreds of years.

3. **Evaluating the Harmfulness**:
- While all options contribute to environmental pollution, the key factor is whether they are biodegradable or not.
- Non-biodegradable chemicals pose a long-term threat as they accumulate in the environment, affecting ecosystems and human health.

4. **Conclusion**: Based on the analysis, the most harmful type of environmental pollutant is **Option D: Non-Biodegradable Chemicals**.

### Final Answer:
**The most harmful type of environmental pollutants are non-biodegradable chemicals.**

---