Euglenoids e.g Euglena are found-

Options

A. In fresh running water
B. In fresh stagnant water
C. In marine environment
D. In both fresh and marine water

Answer

**Step-by-Step Solution:**

1. **Understanding Euglenoids**: Euglenoids, such as Euglena, are unicellular organisms that belong to the kingdom Protista. This classification is important as it helps us understand their habitat.

2. **Identifying the Habitat**: Euglena is primarily found in freshwater environments. They thrive in areas where there is still or stagnant water rather than in fast-moving water bodies.

3. **Analyzing the Options**:
- **Option A**: Fresh running water - Euglena are not commonly found here.
- **Option B**: Fresh stagnant water - This is where Euglena are predominantly found.
- **Option C**: Marine environment - Euglena are not typically found in saltwater.
- **Option D**: Both fresh and marine water - This is incorrect as they are not found in marine environments.

4. **Conclusion**: Based on the analysis, the correct answer is **Option B: Fresh stagnant water**.